Thank you very much for your support. Cutom domain works but one question remains:
More than 48h ago, I created the following redirect in my DNS zone: arru.xyz ->permanent redirect (301) -> www.arru.xyz
but https://arru.xyz does not work.
Is it someting you can fix on your side?
I cannot add a CNAME entry for arru.xyz (my DNS server returns me an incompatibility error because of the other NS and MX entries for arru.xyz). I can only add an A entry. Does miraheze support that?