See @linuxphones.
I have PP and PPP. I run ArchLinux.
PP is slow, but the battery lasts a bit better then PPP. PPP is more powerful, but CPU is too hungry and the phone heats a lot.
If you need long battery life or you type a lot, then buy with the Pine keyboard. It's chunky and have some quality issues, but I would say it worth it.
Software currently immature. I would recommend buying only if you are a very experienced user.
I have a pinephone (not pro) collecting dust, because it's nowhere near as usable for anything, sadly. But I look forward to linux on phones.
I recommend a OnePlus 6 with your choice of linux on phones to be honest.
IMO the most functional pine64 gadgets are the pinetime and pinebook pro, those you can daily drive. The phones are not ready yet, they are good devices to play with but I wouldn't use them as a daily driver, you could miss an important text or phone call and you want a reliable phone in case of an emergency. If you just want a cheap phone that doesn't spy on you I would get a 'dumb' phone.
I own a Pinephone and it wasn't ready for daily driving. Even the battery issues meant that when sleeping, phones wouldn't always wake to receive a call which can be critical. Software is still quite immature, but I would consider buying a Pinephone Pro from them in future as happy with hardware side of things. It will get there, and it's cool to see the progress, in the end, I went with a Pixel with GrapheneOS (degoogled android) which is pretty reliable for the essentials and having access the android apps in a sandbox.
If you're looking for a daily driver, it's probably the best bet right now.
You can try one of the phones that are supported by Ubuntu Touch. I don't know how good it runs but there are several cheap (= old) phones on the list.
Pine hides their hobby-grade hardware behind in-development software. I owned both a PBP and PPP and much as I'd like to say otherwise, really can't say anything to recommend either.
Chiming in to say that my Fairphone 4 worked well with Ubuntu Touch, though I have since come to the conclusion that Waydroid doesn't really work for my usage due to many social apps not integrating well with notifications, as well as missing AGPS support, so I am back on Android with CalyxOS. If you find that GNU/Linux is not daily-driveable for you, I can definitely recommend that.