The same behavior is seen with google chrome.

I can paste to fields in the Right Hand Side with ctrl-v (not ctrl+shift+v) or the browser's right button menu.

I can copy from any of the 3 terminal windows.

+1

+1 on centos7 + firefox

Well I found the cause is the function navigator.clipboard.readText, which is undefined in firefox. After some searching I found more info on https://developer.mozilla.org/en-US/docs/Web/API/Clipboard/readText

Firefox only supports reading the clipboard in browser extensions, using the "clipboardRead" extension permission.

+1

The same behaviour is present with Microsoft Edge on Windows.

+1 with Chrome / FireFox / Safari on MacOS

+1

I also ran into this with Firefox on Arch Linux (Xorg). Here is a work around that worked for me in X11. You can bind it to a key combination or setup some other convenient way of calling it in your WM:
xclip -selection clipboard -out | tr \\n \\r | xdotool selectwindow windowfocus type --clearmodifiers --delay 25 --window %@ --file -

+1 with Chrome

+1 with brave

We are using firefox on Ubuntu 20.04, and this is in my opinion the biggest issue with gdbgui currently that makes it hard for me to recommend its use in our organization. Not being able to paste into the gdb window makes it extremely tedious to type really long commands/paths into it and slows down productivity.

+1 no developer to fixing?

I have the same issue with both Firefox and Chrome in Win11.