Looking up
qt.qpa.xcb: X server does not support XInput 2
I discovered
https://community.rstudio.com/t/x2go-and-rstudio/29704/5
which linked to
https://wiki.x2go.org/doku.php/wiki:development:glx-xlib-workaround
but following the directions for Ubuntu, I get:
E: You must put some 'source' URIs in your sources.list
Moreover, the directions are for Ubuntu 14 and we're on 20, so I'm not even sure the directions are up to date if, indeed, the problem with x2go still exists after all this time.