New motherboard - ANX firmware won't flash.
Okay, so I did it! 
I gave up yesterday not long after I posted this message, and decided to give it a try again just now. What I did:
- Download latest Mobian nightly (specifically build mobian-pinephone-phosh-20201223), flash it to micro-SD card, boot from it with a USB-cable connected, supplying only power (no data!)
- Walk through intro wizard, connect to wifi
- Did not log into phone through SSH, but instead went straight to the wiki article describing how to flash the ANX firmware using Firefox on the phone
- Copy-pasted the commands from the webpage into a terminal (King's Cross) on the phone
- Profit! That was all there was to it
All of the kill-switches were turned on during this process. I did not get any feedback of the flash actually being successful, but since I got only errors previously and none of those (or other messages) this time I'm just going to assume all went well.
I gave up yesterday not long after I posted this message, and decided to give it a try again just now. What I did:- Download latest Mobian nightly (specifically build mobian-pinephone-phosh-20201223), flash it to micro-SD card, boot from it with a USB-cable connected, supplying only power (no data!)
- Walk through intro wizard, connect to wifi
- Did not log into phone through SSH, but instead went straight to the wiki article describing how to flash the ANX firmware using Firefox on the phone
- Copy-pasted the commands from the webpage into a terminal (King's Cross) on the phone
- Profit! That was all there was to it
All of the kill-switches were turned on during this process. I did not get any feedback of the flash actually being successful, but since I got only errors previously and none of those (or other messages) this time I'm just going to assume all went well.
PinePhone (BH 2GB + CE 3GB) // RockPro64 4GB (rev. 2.1) - OMV NAS // PineH64 3GB (model B) - off-prem OMV NAS // Pine64-LTS 2GB (rev. 1.2 + Playbox) - Domotics server