The irony is that CopperheadOS officially only runs on... Google Pixel devices. Yes, Google Pixel devices.
If you use something like microG, all it is is a FOSS implementation of Google Play Services. You're still using Google.
I'd like to see Nextcloud become a drop-in replacement for Google Play Services. They already got Contacts, Photo and Storage support; just needs things such as a distributed Play Store and a Search Engine (SearX?).