I have and use several older Macs stuck as far back as Catalina. But I don’t think I’ll truly be needing iCloud services on those systems. I’ll definitely be trying out ADP as soon as a few days go by without hearing about anything dramatic with these updates.
IMHO the writing is on the wall for local iOS backup to Mac. Looks like Apple has finally successfully bullied me into submission with their most recent shenanigans. If ADP works well and holds its promises, I will be moving to iOS iCloud backup (considering the base 5GB iCloud will suffice for my humble iPhone backup needs). I need only backup so I’ll probably be just fine, but I’m afraid the iMazing crowd is effed.