Is there a workaround for this problem while this is not merged yet?

@GamesByFelix
This patch will just clean keystrokes string that vimgolf shows you after a challenge has been completed.
Until it will be fixed on server side, keystrokes string that is submitted to server should be filtered as well.
To do this you need to add these 2 lines to /usr/lib/ruby/gems/3.4.0/gems/vimgolf-0.5.0/lib/vimgolf/cli.rb

    def upload?(challenge)
+      VimGolf.ui.warn "Cleaning up input keys..."
+      %x( sed -i -e 's/\x80\xfd\x6d//g' #{challenge.log_path} )

      VimGolf.ui.warn "Uploading to VimGolf..."