OX Appsuite: User missing in context, USR-0015

From last posts (and respective answers) I learned, that it is a good idea to NOT use the App Center, but to install required app packages (groupware in my case) from scratch, using whatever help comes from ucs (e.g. LDAP). I’ve done so with SOGo, this went fine, took me like six hours until I figured everything out.
Im testing lot’s of different groupware packages, so I thought I could go the easy way (one click) and just install OX App Suite from the App Center.
That was to no good… I allways (second try, tried different approaches) run into this error:


Previous posts on the issue are not very helpfull, they are outdated and paths mentioned there do not even exist in current versions of UCS.
Are App Center Apps ever tested? I ran into issues with nextcloud as well. My feeling is, lot’s of Apps don’t even install correctly on clean installs of UCS. Why is that so? If I have to learn so much about OX App Suite as to debug similar issues myself, I might just install from scratch (without app Center), this way I know, what I’ve done…
Any help appreciated