I just tried to configure the extended ACL in AcyMailing Enterprise (8.7.3) and I cannot find the Group "Administrator".
When I create a new group, it appears in the list, and I can set access for it, so I could work around this by creating a group that inerits from Administrator though, but I think it's a bug.

Hi,

for bug reports, it is better to open a support ticket

The developers are not monitoring the forum at all

I will alert them about this issue, because I was able to confirm it on my test installation