Thinlinc Client profile chooser ends session

Brand new install of Thinlinc server (Ubuntu 18.06.04, x86_64). Both web client and Thinlinc client exhibit exactly the same behavior: connect to server, enter login credentials, get presented with the profile chooser window. Pick one, any one, doesn’t seem to matter. Press “start”, get “starting Thinlinc session”. At this point, web interface falls back to asking for U/P. Thinlinc client crashes. Clients on OSX Sequoia. Nothing useful shows up in the server logs that I can see.
How to proceed?

Hi @rlmalisz,

If you’re able to upgrade to a more recent version of Ubuntu, then ThinLinc is known to work well with these. Otherwise, one place to check for clues would be the session startup log file at the following location:

/var/opt/thinlinc/sessions/<username/last/xinit.log

Is there anything there which might suggest what is going on?