BAD News!
SIM is gone again!
I think it has to do with the fact that I deactivated SIM Slot 2 in Settings. But I'm not sure. Doesn't look like I am able to switch tomorrow.

Does anybody know where the config file for SIM Cards is?

Is it possible that your SIM card or your SIM holder are damaged? I think the SIM settings are greyed out when no SIM is detected. Do you have a way to try another SIM maybe?

Video playback issue (also posted on TJC):

Most native applications fail to decode any video or stream on my device. I initially thought it was due to the port, but Fellfrosch and Mosen do not have the same issue despite running the same version of the port. I got this issue right after flashing the OS, before doing any tweaks, so I don't know what makes the difference between me and them.

Microtube will crash softly and return to the search results. Twitchtube just never ends buffering, and Twitter videos do not start. Local files fail in Media player as well as in Pico Player. LLSVideoplayer says the following:

"Could not configure supporting library. The video cannot be played due to a problem allocating resources."

Music works.

The only applications that can play local videos so far are Kodi and Sailfish browser (Youtube), however Sailfish browser still fails to play Twitter videos. If I install Ubu chroot and try to play videos in the Ubu Chromium browser from both Youtube and Twitter sources, everything works just fine.

I checked Gstreamer1.0 and confirm it is installed. Could anyone help me by telling me where to start for troubleshooting?

Some output from command line:

I don't think the SIM holder is damaged. I had no problems with Android. SIM worked at the beginning. After fiddling around it stopped working. Same after the reflash. It worked for a few hours and at some time I recognized that it is gone. I have two SIMs both work without problems in my XperiaX. But they don't work anymore in the Pro1 it doesn't matter on which place I insert it. I'm almost sure, that this is software related. If you want to try it yourself, please disable tray two and restart the device.

Did that directly after flashing 3 days ago and my SIM1 is stable.
But i never had a 2nd sim in SIM2 during sfos period, always the sd-card from flashing.
Only tested DualSim shortly on Android.
Maybe try reflash and do like i did, disable slot 2 from start. I did only for cosmetic reasons so the empty icon disapears from status bar. But maybe it is even a workaround for general SIM2 problem on sfos you discovered just now?
My install is quite fleshed out already and i do not want to reflash and setup again just to try :/

Grrrrrrr....
Reflashed an SIM Card is here again. So it's definitely a Software problem.
I will leave my hands from the SIM setting and will install all the stuff I already had installed - always having an eye on my SIM!

I felt like watching an action movie or following a commando squad preparing to a mission while I read the beginning posts for this thread. Nice.

Not sure if related, but I have had quite a lot sim card problems with Pro1 @Android. It prompts pin code too often. People said I should try with another sim card, so I ordered new one today. But I'd say it's possible there is some typical fault related to sim cards, too.

I mentioned the SIM holder too because the SIM card could just work very well in another phone, but be badly inserted in the Pro¹ (if the holder is twisted or something). However, if the SIM immediately shows up every time you flash, then I don't know. I have no second SIM at the moment in my Pro¹ because I use a SD, but I disabled SIM2 in the settings and rebooted, and no issue so far.

My main "isolated" issue is the video thing posted above. :<