If use ssh -X or ssh -Y and start ardour and then add a JUCE VST3 plugin, then ardour will crash with the following message:
PluginWindow deleted for 0x5555628cf340 The program 'ardour-6.6.87' received an X Window System error. This probably reflects a bug in the program. The error was 'BadRequest (invalid request code or no such operation)'. (Details: serial 56 error_code 1 request_code 130 minor_code 2) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.)
That message was with the JUCE Simple Gain plugin included with the sdk. Seems to happen with any JUCE VST3 plugin, and it has been verified with different uses on different linuxes.
Non-JUCE VST3 plugins such as Stienberg host checker and Surge Synthesizer Team · GitHub will work without crashing.
This has been reported to Ardour (JUCE plugins crash Ardour With X11 Forwarding - Linux - Ardour), but at this point it seems like the fix lies on JUCE’s side.
Note that another linux VST3 host “Carla” can load JUCE plugins over X11 forwarding, however according to x42 Carla process-separates the GUI which adds some overhead.