R4Ghidra provides integration between Ghidra and Radare2. It allows you to connect Radare2 to a running Ghidra instance, leveraging the power of both tools together. This plugin was originally known as ghidra-r2web, and has been rebranded and improved as R4Ghidra.
The plugin registers a new menu item under the Tools menu of Ghidra's Code Browser to start/stop the embedded web server. From there you can use r2's connection syntax to connect to Ghidra from Radare2.
For headless usage, see the README.md file in the plugin directory.