< Still move outside from Google services
Does Proton Mail provide CardDAV for contacts? If so, there's an adapter program (DAVx5) that lets you sync to Android. It also syncs calendars with CalDAV.
I use Nextcloud for all the things you're migrating, but I haven't looked at the pricing and policy of any of the cloud hosts for it.
For CardDAV from Proton Mail, I don't thing so, since Proton Mail mostly don't use standard protocols for security/privacy issues.
For Nextcloud (or Owncloud), it can be a solution, I have to see if I can find a Nextcloud/Owncloud hosting that does not cost too much and can fill my needs.