It took me a while to find, but the newest, best supported phones on the device list are
PINE64 PinePhone Pro (2021)
Fairphone 4 (2021) (partial call support)
PINE64 PinePhone (2020)
Purism Librem 5 (2020)
SHIFT SHIFT6mq (2020)
The pixel 3a is not well supported and has problems with wifi, battery, audio, camera, calls, and NFC, so IMO don't base your impression of PostmarketOS on the pixel3a.
Probably because of misunderstanding the project, and thinking it has something to do with Go (the language). Or, maybe not. But programmers can be really uncreative when naming projects; <language><function> is a pretty common naming scheme.
Not to be an asshat about it, but this is what the title reads to me. I’d love a Linux mobile distribution, but really what that’s asking for is: optimized mobile driver kit for an open hardware platform, and the ability to manufacture them at an economy of scale to deliver quality without paying out the ass for. I feel like this is difficult because that development time required to have a stable software and the hardware itself would require tons of money, so one would have to be sacrificed since FOSS devs don’t really have a lot of money… since they do it for free.
Never heard of FuriLabs, looks really cool. How open is the OS/hardware? Could be my next phone... though I'd love to see an immutable approach so I can't be left with a broken system after an update.