X2Go no longer works in 22.04, black screen, then closes

Question

X2Go with MATE desktop used to work fine, but after upgrading to 22.04 it has broken, and I haven't been able to fix it for months. If I try to connect with MATE (from Windows X2Go client), it shows a "New session started" popup and then shows a blank window briefly, and finally 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 (and nothing in dmesg if I try the "Terminal" session type).

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

If I try to connect to "Terminal", on the client, in the folder C:\Users\[Client username]\.x2go\S-[Server username]-50-1672416167_stRTERMINAL_dp32 there is a file named sessions that contains:

Loop: WARNING! Unrecognized session type 'unix-kde-depth_32'. Assuming agent session.
Auth: WARNING! Failed to read data from the X auth command.
Auth: WARNING! Generating a fake cookie for X authentication.
Loop: WARNING! Could not retrieve the X server authentication cookie.

and a file called session.log that contains:

NXPROXY - Version 3.5.0
Copyright (C) 2001, 2010 NoMachine.
See http://www.nomachine.com/ for more information.
Info: Proxy running in client mode with pid '33776'.
Session: Starting session at 'Fri Dec 30 11:02:50 2022'.
Info: Connecting to remote host 'localhost:50767'.
Info: Connection to remote proxy 'localhost:50767' established.
Info: Connection with remote proxy completed.
Warning: Unrecognized session type 'unix-kde-depth_32'. Assuming agent session.
Warning: Failed to read data from the X auth command.
Warning: Generated a fake cookie for X authentication.
Info: Using ADSL link parameters 512/24/1/0.
Info: Using cache parameters 4/4096KB/8192KB/8192KB.
Info: Using pack method '16m-jpeg-9' with session 'unix-kde-depth_32'.
Info: Using ZLIB data compression 1/1/32.
Info: Using ZLIB stream compression 4/4.
Info: No suitable cache file found.
Info: Forwarding X11 connections to display 'localhost:0'.
Session: Session started at 'Fri Dec 30 11:02:50 2022'.
Info: Established X server connection.
Info: Using shared memory parameters 0/0K.
Session: Terminating session at 'Fri Dec 30 11:02:53 2022'.
Session: Session terminated at 'Fri Dec 30 11:02:53 2022'.

and a file called options that contains:

nx/nx,root=/cygdrive/C/Users/[Client username]/X2GO~1,connect=localhost,cookie=ecfd5c17918a53bcfa5a66a50eba7712,port=50767,errors=/cygdrive/C/Users/[Client username]/X2GO~1/S-C536~1/sessions:50

On the server, I get nothing in ~> tail -f $HOME/.xsession-x2go-errors, nothing new appears in ~/.x2go, and ~> tail -f /var/log/syslog | grep x2go says:

Dec 30 11:02:49 shuttle /usr/bin/x2gostartagent: successfully started X2Go Agent session with ID [Server username]-50-1672416167_stRTERMINAL_dp32
Dec 30 11:03:23 shuttle /usr/bin/x2gosetkeyboard: /home/[Server username]/.x2go/C-[Server username]-50-1672416167_stRTERMINAL_dp32/keyboard did not appear within 30s after agent startup

I also tried uninstalling and reinstalling every x2go package on the server, but that didn't fix it.