Wow -- I think that's the solution! I just added this option and restarted the Client -- now "htop" shows a running veyon-server ... I can't test it in our productive environment at the moment but it looks good so far! Thank you!
Mixing operating systems, architectures (32/64 bit) and OS versions should work flawlessly when running an identical version of Veyon on all computers so I wonder what's the issue here. Does the behaviour change when installing the 32 bit version on a student computer (even though it should not be necessary)? Please note that you have to import the settings again after switching to the 32 bit version since it uses a different section of the registry for storing the settings.