I've tried:

    Ubuntu Touch
    Mobian (phosh)
    PostmarketOS (sxmo, phosh)
    Manjaro (Phosh, Plasma and Lomiri)

And multiple release versions of each; using multiple different sdcards as well as the on-board memory.

The only OS that doesn't exhibit the reboot/black-screen issues for me is the one used to allow flashing of the device over USB.

The factory test software works, all of the different OS variants; so if there is a hardware issue the factory test software isn't able to detect it. Notably, I've left the test software running without issue.

I've even tried turning off all the hardware dip switches.

Interesting, but if you really are enthusiastic about the pinephone than perhaps try to order another motherboard (I’m thinking about it because the older has only 2 GB of ram)

I've got the Manjaro CE version, so it should be new enough. I'm also not flush wish cash, so... Yah, I'll be buying diapers for my toddler, not a motherboard that may or may not work.

It's a shame, 'cause I really like the concept, and bought it for myself as a birthday gift. Thought it would be a fun project to hack on.

Yeah, I hear you and I am sad that your unit probably has some issue.. perhaps writing an email asking for a replacement?

I'll give that a shot, but AFAICT from the forum discussions, Pine isn't to amenable to shipping replacements without paying for them.