It's possible, but a huge PITA. Learning how to do it, that is. Once you know all the magic incantations and have your potions and elixirs available, it's easy enough.
Most of the "how to" guides don't mention all the little crap you need to know so it takes a lot of trolling through forums to find why this next step isn't working.
I have a galaxy phone but haven't pursued the idea of installing grapheneOS on it as I thought it would be impossible. Please share you arcane knowledge of the unholy incarnations.
I'm able to use Organic Maps with RH Voice with the sandboxed Google Play + Android Auto Graphene uses for my travelling/cycling/Public-transit map needs.
Mint Mobile. I'm fine with 5GB/5G:$15/month ~$185/year. 🤘😁.
I download flac songs/albums for off line use with Tidal when not streaming on WiFi.
PipePipe for YouTube/etc stuffs. 720p or background playback to save bandwith/battery isn't bad.