Daily-Driving OnePlus 6 with PostmarketOS
Recently I've purchased a used OnePlus 6 phone, which is capable of running mainline Linux. Replacing Android with PostmarketOS took a bit of work, but eventually I've got everything working.
Surprisingly, things like GSM, mobile internet, calls -- all work out of the box. And the Phosh interface is good looking and snappy enough that it compares to a 2-3 year old andoid phone.
If you're a Linux enthusiast and would like to have some freedom on the mobile -- give it a try! You can get the phone on Ebay for less than $100.
If you do this -- note that before erasing Android, you need to apply all updates. It wasn't obvious to me when I first started the phone and the "About" page has shown that I'm "up to date". You need to be really really sure that it's the case, otherwise you would have old microcode blobs in the screen controller and potentially other chips, and you won't be able to start Linux normally.
I made this mistake, and had to follow a lengthy and convoluted process of using a leaked MSMDownload tool to unbrick the device, and apply fresh updates. If you find yourself in this situation, follow that link. Apparently, this is what official service technicians would do to reflash the OS from scratch.