It's really much harder than you'd imagine it'd be before starting if you're hoping to retain the same level of convenience. I'd say nearly impossible.

I moved my phone to Graphene last week and have spent countless hours getting things to work and finding ways to do things without Google's various apps and there is always a concession to be made. You can install those G-apps but that's the whole point so you have to keep accepting things like no RCS in messages, no touch-to-pay, no reliable speech synthesis, a bunch of non-working apps if they rely on the play services, no whole-phone backup and restore, etc. The list is very, very long.

I'm not Google-free on it but with sandboxed and permission-stripped G-apps, I'm hoping I'm not leaking my data to Google.

Start at least. Perfect is the enemy of good enough.

Self hosting, Hetzner, INWX, mailbox/posteo/infomaniak/proton and Ubuntu fix pretty much most scenarios.

I really don’t think it’s any difficult for individual, tech savvy users