diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 72937128..45645123 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -284,17 +284,17 @@ jobs:
           cl -MT -J -O2 -W3 -WX %DEFS% -c %H%\vendor\zlib\*.c
           link -lib -out:zlib.lib *.obj
           @REM ===== build zstd =====
-          cd %BDIR%\zstd
-          set s=%H%\vendor\zstd\lib
-          cl -MT -J -O2 -W4 -WX -DDYNAMIC_BMI2=0 -DZSTD_DISABLE_ASM %DEFS% -c %s%\common\*.c %s%\compress\*.c %s%\decompress\*.c
-          link -lib -out:zstd.lib *.obj
+          @rem cd %BDIR%\zstd
+          @rem set s=%H%\vendor\zstd\lib
+          @rem cl -MT -J -O2 -W4 -WX -DDYNAMIC_BMI2=0 -DZSTD_DISABLE_ASM %DEFS% -c %s%\common\*.c %s%\compress\*.c %s%\decompress\*.c
+          @rem link -lib -out:zstd.lib *.obj
           @REM ===== build UPX =====
           cd %BDIR%\upx
           set s=%H%\src
           cat .GITREV.txt
           set /p GITREV=<.GITREV.txt
           set sources=%s%\*.cpp %s%\check\*.cpp %s%\compress\*.cpp %s%\console\*.cpp %s%\filter\*.cpp %s%\util\*.cpp
-          cl -std:c++17 -Zc:__cplusplus -EHsc -J -O2 -W4 -WX -DUPX_VERSION_GITREV="""%GITREV%""" -DWITH_ZSTD %DEFS% -I%H%\vendor -I%H%\vendor\boost-pfr\include -Feupx.exe %sources% %BDIR%\ucl\ucl.lib %BDIR%\zlib\zlib.lib %BDIR%\zstd\zstd.lib /link setargv.obj
+          cl -std:c++17 -Zc:__cplusplus -EHsc -J -O2 -W4 -WX -DUPX_VERSION_GITREV="""%GITREV%""" -DWITH_ZSTD=0 %DEFS% -I%H%\vendor -I%H%\vendor\boost-pfr\include -Feupx.exe %sources% %BDIR%\ucl\ucl.lib %BDIR%\zlib\zlib.lib /link setargv.obj
       - name: 'Make artifact'
         shell: bash
         run: |
diff --git a/.gitmodules b/.gitmodules
index 7b2f2bc9..33f9f2d5 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,8 +1,3 @@
-[submodule "vendor/boost-pfr"]
-    path = vendor/boost-pfr
-    url = https://github.com/upx/upx-vendor-boost-pfr.git
-    branch = upx-vendor
-    shallow = true
 [submodule "vendor/doctest"]
     path = vendor/doctest
     url = https://github.com/upx/upx-vendor-doctest.git
@@ -13,11 +8,6 @@
     url = https://github.com/upx/upx-vendor-lzma-sdk.git
     branch = upx-vendor
     shallow = true
-[submodule "vendor/rangeless"]
-    path = vendor/rangeless
-    url = https://github.com/upx/upx-vendor-rangeless.git
-    branch = upx-vendor
-    shallow = true
 [submodule "vendor/ucl"]
     path = vendor/ucl
     url = https://github.com/upx/upx-vendor-ucl.git
@@ -33,8 +23,3 @@
     url = https://github.com/upx/upx-vendor-zlib.git
     branch = upx-vendor
     shallow = true
-[submodule "vendor/zstd"]
-    path = vendor/zstd
-    url = https://github.com/upx/upx-vendor-zstd.git
-    branch = upx-vendor
-    shallow = true
diff --git a/Makefile b/Makefile
index 1e5ecf01..18b57bed 100644
--- a/Makefile
+++ b/Makefile
@@ -134,7 +134,7 @@ build/extra/cross-windows-mingw64/%: UPX_CMAKE_CONFIG_FLAGS += -DUPX_CONFIG_DISA
 # check git submodules
 #***********************************************************************
 
-SUBMODULES = boost-pfr doctest lzma-sdk rangeless ucl valgrind zlib zstd
+SUBMODULES = doctest lzma-sdk ucl valgrind zlib
 
 dummy := $(foreach m,$(SUBMODULES),$(if $(wildcard vendor/$m/[CL]*),$m,\
     $(error ERROR: missing git submodule $m; run 'git submodule update --init')))
diff --git a/src/check/dtx_boost_pfr.cpp b/src/check/dtx_boost_pfr.cpp
index bc565f48..954a5cae 100644
--- a/src/check/dtx_boost_pfr.cpp
+++ b/src/check/dtx_boost_pfr.cpp
@@ -24,7 +24,7 @@
    <markus@oberhumer.com>
  */
 
-#if DEBUG
+#if DEBUG && 0
 #ifndef WITH_BOOST_PFR
 #define WITH_BOOST_PFR 1
 #endif
diff --git a/vendor/boost-pfr b/vendor/boost-pfr
deleted file mode 160000
index f626eb1a..00000000
--- a/vendor/boost-pfr
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit f626eb1a31c2b685eddebc7738c771ad60989e0f
diff --git a/vendor/rangeless b/vendor/rangeless
deleted file mode 160000
index c283c97b..00000000
--- a/vendor/rangeless
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit c283c97b47252e20ca0307f5a5641c490419e23b
diff --git a/vendor/zstd b/vendor/zstd
deleted file mode 160000
index 2eed0e3a..00000000
--- a/vendor/zstd
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 2eed0e3abae48b4839a73fc85a4061ff5735a88a