"smartphone" doesn't matter. it is a computer that runs software. the only question is who controls that software? free/libre software is by definition one that you control. and what you described means that you dont control your device.
so advices: easy way is to just install lineage os or graphene or some other open source android version. you will control it. i dont advice to install google play services.
other advice: you can get a sony phone because it can run sailfish os. also i believe those are great. otherwise install open source android, lineage or something.
sailfish has android emulator (it costs money) but sailfish is not android. it is a linux/qt based system. very polished. not as polished as open source android, but it is fast, lightweight and beautiful. native sailfish apps arent feature rich but do you really need feature rich? then you can get more apps from fdroid store and use android emulation layer.
other, better but harder option: get a device which is well supported by postmarketos.
postmarketos has several user interfaces but neither of those is what you have used to. i believe it is the best option but you must prepare yourself to be able to change. most probably you wont have a working camera. thats ok, i live like that.