Multiple issues with the Pinephone

[MTXP]

Thanks again man, this is exactly what I needed. Sadly though, connecting the charger doesnt change much if anything. Arch linux HDMI is not working at all, and the default PP OS is only streaming the home page (just like the first time I tried it). Clicking on any app doesn't show the app there and of course the mobile screen is jittery and very hard to navigate. I'm not sure but I think plugging it in the charger helped stabilize the phone in terms of battery and it got rid of the constant brightness changes.

The stock os (manjaro plasma which comes preinstalled) is at the moment awful and horrible outdated.

I suggest that try Arch Phosh and pmos phosh.
Power off completely -> switch the modem kill switch off (= power modem off) -> boot the PP and try again.
Also make sure you have tow-boot installed: https://tow-boot.org/

Good news! I turned the modem off and didn't see any improvement, but then I tried plugging in a different monitor, one that doesn't even have HDMI for which I had to buy an adapter a couple days ago, and it worked! It makes me kinda uneasy that I will never know if certain monitor or TV works or now until I try it, but at least I have something to work with now. And I find it strange that a DVI monitor worked better than a newer, HDMI TV. Thanks for the tips so far. Speaking of which, what's the tow-boot for?