Thank you very much, it’s great that you took the time to gather all this information here. I’m sure this is going to be very helpful for German PPM users.
A couple of comments:
This is a known bug which is already being worked on. Please see this thread: Current Bug / Planned Features list
There are apps you can install to force landscape mode. This should help with the rotating screen. See this thread: Default "Force landscape" or add option to change the orientation
Currently, Firefox doesn’t use hardware decoding which makes it unecessarily slow. This is also a known bug, which is being worked on. It’s in the list I linked above.
Hope this helps.