One thing i can not get reliably to work is voice calling. Under SXMO i can establish a call but get no audio (and i get the error message "We failed to establish call audio"), under Phosh (yeah, i flashed the device multiple times... but more on that later) i CAN get working calls but not reliably. After spending a few days getting it to work and getting pretty frustrated a thought crept into my mind and i dug out the emails of the coworker that owned the device previously, and yes, a similar behaviour was wat lead to the device ending up in the "crap electronics" box in my office in the first place. Hmm... ok, lets put "voice calling" a few steps down on the priority ladder.
So, for the moment i ended up with a setup where i have my old anroid phone with its crappy, battery for voice calling and as camera device and the Oneplus 6 for... uhm... everything else.
Additionaly i have also installed Gimp and Libreoffice on the device because i had this neat little idea of accessing it over a VNC session... which works surprisingly well. Overall i observed that having a whole Linux distribution running on my "Phone" leads to me using my Laptop less every day. It is surprisingly conveniant (even with the tiny on screen keyboard) to hack something together directly while having the idea sitting on the couch or in the train instead of my traditional approach.
The next step will be to use an old Raspberry Pi B sitting somewhere in my drawer to use as a terminal for the phone. I think the combination of a really slow Pi and a pretty powerfull "mini workstation" caryable in your pocket is a really nice thought.