Isn't there a Google Android source code release that all of these are based on?
Android is from Big Bad G.
Android Open Source Project (AOSP) is their FLOSS release.
Like CentOS for RHEL.
CyanogenMod is based on AOSP.
The compagny behind it died a few weeks ago [and I'm not laughting at them].
The project has been forked, community driven only.
Now rebranded LineageOS.
Replicant is based on CyanogenMod.
Il is fully deblobbed (drivers, bloatware ...), like Pandora for Arch, Triskel for Ubuntu, Libreboot for Coreboot ...
Replicant team strongly suggest to use FLOSS repositories only (F-Droid) to keep the device free as the bird.
But I doubt it forbids users to use Google Play store if they really want to do so.
There might be some incompatibilities though ...
Those information are subject to caution since my knowledge here comes from my readings only.
I never owned an Android device and thanks to the Pyra, I may never have to.