I've been using Intune at home because I use it at work too and I already had a personal O365 setup. It was nice to have a fully owned instance when I was learning it, but I'm trying to scale back my costs now so something like this might just suffice.
Android only:
https://github.com/h-mdm
Apple only:
https://github.com/cmdmnt/commandment
Both:
https://github.com/flyve-mdm