Problems administrating subwikis using subdomains

Hello,
I’m currently trying to set up a new XWiki Instance with two subwikis, preferably using subdomains.
The setup is as follows:
Debian 12
XWiki 16.10.8 (installed from xwiki-lts.list)
Installed packet xwiki-xjetty-mariadb, but using a external MariaDB server
Using Apache as a proxy with an apache.conf like this. Including a wildcard certificate for the used domain.

Main wiki:
xwiki. our. domain. com
Subwikis:
subwiki1. xwiki. our. domain. com (Only Global Users)
subwiki2. xwiki. our. domain. com (Global and Local Users)
For both subwikis the following options are activated:
Prevent unregistered users from viewing pages, regardless of the page rights
Prevent unregistered users from editing pages, regardless of the page rights

Everything seems to be working fine when using the path based subwiki style. The only thing I noticed is that I’m not able to change the membership type as described here. The Options described are not shown, regardless which initial membership type was selected.

My main issues appear however after changing to the subdomain style by changing the following parameters:
in /etc/xwiki/xwiki.properties
url.standard.multiwiki.isPathBased=false
in /etc/xwiki/xwiki.cfg
xwiki.virtual.usepath=0
xwiki.authentication.cookiedomains=xwiki.coll.mpg.de

Afterwards I have the following issues:

  • I’m not able to administer subwiki1 (Only Global Users) at all as the option in the hamburger menu is not shown. And it doesn’t matter if I use the Wiki Index to change to the subwiki (which keeps me logged in) or log into the subwiki directly.
  • I’m principally able to administer subwiki2, although I’m might have added the local user of the same name as my main admin to the local XWikiAdminGroup at some point. However I’m unable to see any Global Groups or Users.
    Both issue lead me to believe there is some kind of inability for the subwiki to access the main wiki in regards to the rights of the logged in global user. Or some other form of internal communications error.

I would very much appreciate any help or pointer for my problems, as I was unable to find any working solution so far.