So I have anyconnect working now.
In sssd.conf I added:
[domain]
use_fully_qualified_names = True
full_name_format = %1$s@%2$s
and now all users in `who` are user@domain
However, setting it to the following does not change the behavior and gnome_session_binary
is still started as user@domain while all others are user:
[domain]
use_fully_qualified_names = False
full_name_format = %1$s
I can make this work though! I'll troubleshoot a bit longer because I'd prefer
that everyone is just called 'user'