I imagine the following communities can be helpful:
!privacy@lemmy.dbzer0.com
!privacy@programming.dev

But any guide would essentially be:

• Identify what kind of services and products from Google that you use (ex: Android, Google Maps)
• Identify replacements for those services and products (ex: GrapheneOS or LineageOS instead of Android and OrganicMaps, OSMAnd or Magic Earth instead of Google Maps)
• Verify that the replacements work for you
• Make a plan on how to move to the replacements you have identified. (ex: Backup all important data on the phone before changing OS)