[X2Go-User] X2Go no longer works in 22.04, black screen

X2Go with MATE desktop used to work fine, I've been using it for years, but after upgrading to 22.04 a few months ago, it is broken and I don't know how to fix it.

If I try to connect with MATE (from Windows X2Go client), it shows a "New session started" popup, shows a blank window briefly, then closes. On the server, running dmesg --follow at the same time, I see:

[14238.559864] show_signal_msg: 3 callbacks suppressed
[14238.559867] mate-session[129320]: segfault at 7f3200000060 ip 00007f325d65f52f sp 00007fff9ee3b250 error 4 in libgdk-3.so.0.2404.29[7f325d623000+83000]
[14238.559876] Code: 57 82 fc ff 49 8b 9c 24 70 01 00 00 48 85 db 74 4e 49 89 c5 eb 0a 0f 1f 44 00 00 48 85 db 74 3f 48 8b 2b 48 89 de 48 8b 5b 08 <48> 8b 45 08 48 85 c0 74 e8 4c 39 e8 7f e3 49 8b bc 24 70 01 00 00

If I try to use something other than MATE, like "Connection to local desktop" (which also used to work), it shows "Select desktop" with :0 and :1 as options. If I select either, and hit "View Only" or "Full Access", I just get a black window and nothing in dmesg.

Same results from another Windows computer that used to work, so it's a server issue, not a client issue.

https://askubuntu.com/q/1432163/5032