I am not sure it is, but Graphene has an optional sandboxed Google Play Services that does not require signature spoofing and does not require a Google account. I have it installed on a work profile for some proprietary work apps that require it. My main profile contains all FOSS apps that use web sockets or Unified Push(Nextpush on Nextcloud) to deliver notifications.

There is the Google Play compatibility layer on Graphene, so you probably don't need microg - https://grapheneos.org/features#sandboxed-google-play