I mostly use LineageOS (formerly Cyanogenmod) as a starting point, sometimes with a few customisations but often just straight off the 'net. As to app stores,

I mostly use LineageOS (formerly Cyanogenmod) as a starting point, sometimes with a few customisations but often just straight off the 'net. As to app stores, I use F-Droid and Aurora Store (an alternative front end to the Play Store) for those few proprietary apps (mostly the Swedish BankID electronic ID app) I need to have access to. Aurora Store works with anonymous Google accounts, you do not need - and are advised not to use - a real Google account for this. I use MicroG (free software implementation of the Google Services Framework) on a few devices but mostly just do without it.