The Portal currently runs on the same host than on UMC and overtakes/co-uses the sessions of logged in users. In a containerized area the request comes from a different IP than 127.0.0.1 and the session-overtake is therfor prevented. We could make the allowed IP (ranges) which can overtake sessions configurable via UCR.
MR: https://git.knut.univention.de/univention/ucs/-/merge_requests/584
Patch was applied in Bug #43633 *** This bug has been marked as a duplicate of bug 43633 ***