I can confirm this issue in my own environment as well.  X2Go server version is running on CentOS 7.  Affected users are running X2Go client version on Windows 10 (though this may affect other Windows versions as well).

We forced the use of the aes128-ctr cipher yesterday on our cluster login nodes to resolve a security issue raised by our security team.  To do this, we added the following line to our SSH server config file:

Ciphers aes128-ctr

After making this change, several users running the X2Go client on Windows 10 could no longer connect.  We found this bug report, and subsequently reverted the above change, which resolved the issue.

Please note that Linux clients appeared to be unaffected by this issue; I was able to connect from a workstation running X2Go client version on Ubuntu Linux 20.04 without any issues.

Adam Dorsey
NOAA RDHPCS Systems Administrator Site Lead
CSRA / RedLine Performance Solutions, LLC

1000 Galliher Drive, Suite 333, Fairmont, WV 26554
office: (304) 367-2882
cell: (304) 685-9345