I'd love to do this to my phone (Moto G4). However I absolutely need my banking app, and I know it just wont work without Google Play running. Likewise as the article says, Google Maps is a must even with location tracking off. I do switch off as much personal data leakage as I can, but I'm not naive enough to think that Google isn't still collecting data on me.
Unfortunately, I just don't think a free open source phone will full modern functionality is ever going to exist.
Regarding OS there is still hope. Check out e.foundation (formerly eelo).
And puri.sm Librem 5 if you want a linux-based OS (have to wait for android app support for a while still, I think).
There is the Anbox[0] which looks promising.