If you want to use Linux on a phone, I would rather you go with an older device w/ postmarketOS rather than any dedicated "Linux phones" (e.g. Purism) since those tend to not be great values for the money. The OnePlus 6 / 6T are very well supported, but you also have devices like the Pixel 3a series and the Fairphones (which are newer, if you want their repairability. They come with an Android base OOTB) as well.
pmOS + Phosh on the OnePlus 6, from my own testing, has been pretty good. However, the camera drivers are very new (no AF, fixed zoom, grainy, poor dynamic range, etc. Photos look kind of cool, like film-style photography almost), GPS is inaccurate, and battery life isn't the best OOTB (it's an 8 year old device, so super degraded). It's still pretty neat though, and although it's not a daily driver phone for most people (including myself), it's fun to mess around with. I particularly enjoy the ecosystem of mobile games that, although small, is excellent as there is no microtransactions, advertisements, predatory marketing, etc.!