diff --git a/browser/base/content/sanitize.xhtml b/browser/base/content/sanitize.xhtml
index 9de56eef0c5c..a4ec3b5ef9bb 100644
--- a/browser/base/content/sanitize.xhtml
+++ b/browser/base/content/sanitize.xhtml
@@ -38,7 +38,7 @@
     <menulist id="sanitizeDurationChoice"
               preference="privacy.sanitize.timeSpan"
               onselect="gSanitizePromptDialog.selectByTimespan();"
-              flex="1" native="true">
+              flex="1">
       <menupopup id="sanitizeDurationPopup">
         <menuitem data-l10n-id="clear-time-duration-value-last-hour" value="1"/>
         <menuitem data-l10n-id="clear-time-duration-value-last-2-hours" value="2"/>
diff --git a/browser/components/shell/content/setDesktopBackground.xhtml b/browser/components/shell/content/setDesktopBackground.xhtml
index 778285b410e2..53cd586a3c16 100644
--- a/browser/components/shell/content/setDesktopBackground.xhtml
+++ b/browser/components/shell/content/setDesktopBackground.xhtml
@@ -48,7 +48,7 @@
     <hbox align="center">
       <label data-l10n-id="set-background-position"/>
       <menulist id="menuPosition"
-                oncommand="gSetBackground.updatePosition();" native="true">
+                oncommand="gSetBackground.updatePosition();">
         <menupopup>
           <menuitem data-l10n-id="set-background-center"  value="CENTER"/>
           <menuitem data-l10n-id="set-background-tile"    value="TILE"/>
diff --git a/browser/themes/shared/browser-custom-colors.inc.css b/browser/themes/shared/browser-custom-colors.inc.css
index 6554ab79bc6f..ccb41428c7d3 100644
--- a/browser/themes/shared/browser-custom-colors.inc.css
+++ b/browser/themes/shared/browser-custom-colors.inc.css
@@ -12,7 +12,7 @@
     --buttons-secondary-bgcolor: rgb(240,240,244);
     --buttons-secondary-hover-bgcolor: rgb(224,224,230);
     --buttons-secondary-active-bgcolor: rgb(207,207,216);
-    --buttons-secondary-color: rgb(21,20,26);
+    --buttons-secondary-color: rgb(91,91,102);
     --buttons-box-shadow: transparent;
 
     --focus-outline-color: var(--buttons-primary-button-bgcolor);
diff --git a/security/manager/pki/resources/content/clientauthask.xhtml b/security/manager/pki/resources/content/clientauthask.xhtml
index e1fba53d0a88..d597ba7ba21f 100644
--- a/security/manager/pki/resources/content/clientauthask.xhtml
+++ b/security/manager/pki/resources/content/clientauthask.xhtml
@@ -36,7 +36,7 @@
 <!-- The items in this menulist must never be sorted,
      but remain in the order filled by the application
 -->
-<menulist id="nicknames" oncommand="onCertSelected();" native="true">
+<menulist id="nicknames" oncommand="onCertSelected();">
     <menupopup/>
 </menulist>
 <description data-l10n-id="client-auth-cert-details"></description>
diff --git a/toolkit/content/widgets/menulist.js b/toolkit/content/widgets/menulist.js
index d789657b25a9..80f52ccd2b39 100644
--- a/toolkit/content/widgets/menulist.js
+++ b/toolkit/content/widgets/menulist.js
@@ -69,12 +69,10 @@
 
     static get inheritedAttributes() {
       return {
-        "#label-box": "native",
-        image: "src=image,native",
-        "#label": "value=label,crop,accesskey,highlightable,native",
-        "#highlightable-label":
-          "text=label,crop,accesskey,highlightable,native",
-        dropmarker: "disabled,open,native",
+        image: "src=image",
+        "#label": "value=label,crop,accesskey,highlightable",
+        "#highlightable-label": "text=label,crop,accesskey,highlightable",
+        dropmarker: "disabled,open",
       };
     }
 
diff --git a/toolkit/mozapps/downloads/content/unknownContentType.xhtml b/toolkit/mozapps/downloads/content/unknownContentType.xhtml
index 1855395a7408..23dbf623304c 100644
--- a/toolkit/mozapps/downloads/content/unknownContentType.xhtml
+++ b/toolkit/mozapps/downloads/content/unknownContentType.xhtml
@@ -72,7 +72,7 @@
           <radio id="open" label="&openWith.label;" accesskey="&openWith.accesskey;"/>
           <deck id="modeDeck" flex="1">
             <hbox id="openHandlerBox" flex="1" align="center">
-              <menulist id="openHandler" flex="1" native="true">
+              <menulist id="openHandler" flex="1">
                 <menupopup id="openHandlerPopup" oncommand="dialog.openHandlerCommand();">
                   <menuitem id="defaultHandler" default="true" crop="right"/>
                   <menuitem id="otherHandler" hidden="true" crop="left"/>
diff --git a/toolkit/themes/linux/global/jar.mn b/toolkit/themes/linux/global/jar.mn
index ff66282cae5a..eb6c05e8d08d 100644
--- a/toolkit/themes/linux/global/jar.mn
+++ b/toolkit/themes/linux/global/jar.mn
@@ -13,7 +13,7 @@ toolkit.jar:
 *  skin/classic/global/findBar.css
 *  skin/classic/global/global.css
 *  skin/classic/global/menu.css
-*  skin/classic/global/menulist.css
+   skin/classic/global/menulist.css
    skin/classic/global/netError.css
    skin/classic/global/popup.css
 *  skin/classic/global/popupnotification.css
diff --git a/toolkit/themes/linux/global/menulist.css b/toolkit/themes/linux/global/menulist.css
index 3225bea3bcac..10acbf69227c 100644
--- a/toolkit/themes/linux/global/menulist.css
+++ b/toolkit/themes/linux/global/menulist.css
@@ -4,53 +4,6 @@
 
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
-%include ../../shared/menulist.inc.css
-
-@supports -moz-bool-pref("browser.proton.enabled") {
-label {
-  margin: 1px 3px !important;
-}
-
-:host([native])  {
-  appearance: auto;
-  -moz-default-appearance: menulist;
-  margin: 2px 4px;
-  color: -moz-DialogText;
-  font: menu;
-  text-shadow: none;
-}
-
-:host([native]:not([disabled="true"]):hover) {
-  color: -moz-buttonhovertext;
-}
-
-:host([native]:not([disabled="true"]):hover:active),
-:host([native]:not([disabled="true"])[open="true"]) {
-  color: -moz-gtk-buttonactivetext;
-}
-
-:host([native][disabled="true"]) {
-  color: GrayText;
-}
-
-/* Label box */
-
-#label-box[native] {
-  appearance: auto;
-  -moz-default-appearance: menulist-text;
-  -moz-box-align: center;
-  -moz-box-pack: center;
-  color: inherit;
-}
-
-/* Dropmarker */
-
-dropmarker[native] {
-  display: none;
-}
-} /** END Proton **/
-
-@supports not -moz-bool-pref("browser.proton.enabled") {
 :host {
   appearance: auto;
   -moz-default-appearance: menulist;
@@ -99,4 +52,3 @@ label {
 dropmarker {
   display: none;
 }
-} /** END not Proton **/
diff --git a/toolkit/themes/osx/global/jar.mn b/toolkit/themes/osx/global/jar.mn
index a60c21a24206..b6457513908b 100644
--- a/toolkit/themes/osx/global/jar.mn
+++ b/toolkit/themes/osx/global/jar.mn
@@ -14,7 +14,7 @@ toolkit.jar:
 * skin/classic/global/findBar.css
 * skin/classic/global/global.css
 * skin/classic/global/menu.css
-* skin/classic/global/menulist.css
+  skin/classic/global/menulist.css
   skin/classic/global/netError.css
   skin/classic/global/popup.css
 * skin/classic/global/popupnotification.css
diff --git a/toolkit/themes/osx/global/menulist.css b/toolkit/themes/osx/global/menulist.css
index b4cb54e2d03b..98133a8a0bab 100644
--- a/toolkit/themes/osx/global/menulist.css
+++ b/toolkit/themes/osx/global/menulist.css
@@ -4,54 +4,6 @@
 
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
-%include ../../shared/menulist.inc.css
-
-@supports -moz-bool-pref("browser.proton.enabled") {
-label:not([native]) {
-  margin: 2px 3px !important;
-}
-
-:host([native]) {
-  appearance: auto;
-  -moz-default-appearance: menulist;
-  margin: 5px 2px 3px;
-  min-height: 20px;
-  color: -moz-DialogText;
-  text-shadow: none;
-  padding: unset;
-}
-
-:host([native][disabled="true"]) {
-  color: GrayText;
-}
-
-:host([native][disabled="true"]) > dropmarker {
-  padding-inline-start: 7px !important;
-}
-
-/* Label box */
-
-#label-box[native] {
-  appearance: auto;
-  -moz-default-appearance: menulist-text;
-  -moz-box-align: center;
-  -moz-box-pack: center;
-  margin-bottom: 1px;
-}
-
-label[native] {
-  margin: 1px 3px !important;
-}
-
-/* Dropmarker */
-
-dropmarker[native] {
-  display: none;
-}
-
-} /** END Proton **/
-
-@supports not -moz-bool-pref("browser.proton.enabled") {
 :host {
   appearance: auto;
   -moz-default-appearance: menulist;
@@ -95,4 +47,3 @@ label {
 dropmarker {
   display: none;
 }
-} /** END not Proton **/
diff --git a/toolkit/themes/shared/menulist.inc.css b/toolkit/themes/shared/menulist.inc.css
deleted file mode 100644
index 962a7d25fd1c..000000000000
--- a/toolkit/themes/shared/menulist.inc.css
+++ /dev/null
@@ -1,62 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
-
-@supports -moz-bool-pref("browser.proton.enabled") {
-:host(:not([native])) {
-  appearance: none;
-  background-color: var(--buttons-secondary-bgcolor, ButtonFace);
-  color: var(--buttons-secondary-color, ButtonText);
-  border-radius: 4px;
-  padding: 4px 8px 4px 12px;
-  margin: 5px 2px 3px;
-}
-
-:host(:not([native])[size="medium"]) {
-  padding: 6px 10px 6px 16px;
-}
-
-:host(:not([native])[size="large"]) {
-  padding: 8px 12px 8px 16px;
-}
-
-:host(:not([native]):hover) {
-  background-color: var(--buttons-secondary-hover-bgcolor, color-mix(in srgb, currentColor 10%, ButtonFace));
-}
-
-:host(:not([native]):hover:active) {
-  background-color: var(--buttons-secondary-active-bgcolor, color-mix(in srgb, currentColor 20%, ButtonFace));
-}
-
-:host(:not([native]):-moz-focusring) {
-  outline: 2px solid var(--focus-outline-color, -moz-accent-color);
-  outline-offset: var(--focus-outline-offset, -1px);
-  box-shadow: 0 0 0 4px var(--buttons-box-shadow, rgba(10, 132, 255, 0.3));
-}
-
-#label-box:not([native]) {
-  -moz-box-align: center;
-  -moz-box-pack: center;
-  font-weight: 600;
-}
-
-dropmarker:not([native]) {
-  display: -moz-box;
-  appearance: none;
-  width: 12px;
-  height: 12px;
-}
-
-dropmarker:not([native])::part(icon) {
-  list-style-image: url(chrome://global/skin/icons/arrow-dropdown-16.svg);
-  -moz-context-properties: fill;
-  fill: currentColor;
-}
-
-#highlightable-label:not([highlightable="true"]),
-#label[highlightable="true"] {
-  display: none;
-}
-} /** END Proton **/
diff --git a/toolkit/themes/windows/global/jar.mn b/toolkit/themes/windows/global/jar.mn
index a2c43dc59169..a1e663e15585 100644
--- a/toolkit/themes/windows/global/jar.mn
+++ b/toolkit/themes/windows/global/jar.mn
@@ -10,7 +10,7 @@ toolkit.jar:
 * skin/classic/global/checkbox.css
   skin/classic/global/dropmarker.css
 * skin/classic/global/menu.css
-* skin/classic/global/menulist.css
+  skin/classic/global/menulist.css
   skin/classic/global/radio.css
   skin/classic/global/tabbox.css
   skin/classic/global/search-textbox.css
diff --git a/toolkit/themes/windows/global/menulist.css b/toolkit/themes/windows/global/menulist.css
index ceda46b83469..7ca8b28421a9 100644
--- a/toolkit/themes/windows/global/menulist.css
+++ b/toolkit/themes/windows/global/menulist.css
@@ -4,62 +4,6 @@
 
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
 
-%include ../../shared/menulist.inc.css
-
-@supports -moz-bool-pref("browser.proton.enabled") {
-label {
-  margin: 0 3px !important;
-}
-
-:host([native]) {
-  appearance: auto;
-  -moz-default-appearance: menulist;
-  margin: 2px 4px;
-  color: FieldText;
-  text-shadow: none;
-}
-
-:host([native][disabled="true"]) {
-  background-color: -moz-Dialog;
-  color: GrayText;
-}
-
-/* Label box */
-
-#label-box[native] {
-  -moz-box-align: center;
-  -moz-box-pack: center;
-}
-
-:host([native]:not([open="true"]):focus) > #label-box {
-  background-color: Highlight;
-  color: HighlightText;
-}
-
-:host([native]:not([open="true"]):-moz-focusring) > #label-box {
-  outline: 1px dotted;
-}
-
-
-@media (-moz-windows-default-theme) {
-  #label-box[native] {
-    background-color: transparent !important;
-    color: inherit !important;
-  }
-
-  image[native],
-  label[native] {
-    margin-block: -1px !important;
-  }
-
-  dropmarker[native] {
-    margin-top: -2px;
-    margin-inline: 3px -3px;
-  }
-}
-} /** END Proton **/
-
-@supports not -moz-bool-pref("browser.proton.enabled") {
 :host {
   appearance: auto;
   -moz-default-appearance: menulist;
@@ -116,4 +60,3 @@ label {
     margin-inline: 3px -3px;
   }
 }
-} /** END not Proton **/