Thanks for the quick reply - I installed the latest Blissrom and nano 10.0 gapps and got a little further with family link. Now it fails when asking for permissions - I click allow and then it goes to the cancel setup screen as if I had denied the permissions.
Yes I did.
It has to do with Gapps and the version number.
I tried first several NikGapps version which is suggested for this ROM however not one worked.
In the end I remember that I switched to OpenGapps of which I used the ARM64/Android10/Nano version.
I don't know which version number, so you might want to try several version numbers.
It fixed all of my google related problems I had incl. child supervision.