Personally, I would rank them:
- Fairphone (repairable and supports fair materials + working conditions, mobile Linux support is growing too!)
- Jolla (affordable, SailfishOS)
- Shiftphone (repairable, privacy kill switches, not as available or as good value as Fairphone)
- HMD (affordable, repairable, Android)
- Volla (Ubuntu Touch)
- Punkt (closed bootloader, expensive)
edit: Shiftphone moved up. Personally, I think Fairphone is ideal (can run degoogled Android and mobile Linux, repairable, fair production, etc.), Jolla Phone is cheaper than Fairphone and ships with SailfishOS OOTB so is also nice for most people. Those two are probably the easiest recommendation to most people, the others have their own caveats.
Shiftphone is also repairable and has privacy kill switches (unlike Fairphone) but not as good value spec wise, HMD produces cheaper Android devices of questionable quality, and only a few support custom ROMs, Volla is cool if you like Ubuntu Touch but their devices are a bit expensive + not repairable (latter is the main reason why I rank it lower), and Punkt uses a locked bootloader, so custom ROMs are not an option.