@jlabon
Thank you for your fast reply! And thank you also for listing your issues so clearly.
I seem to be facing similar issues when it comes to USB-MTP - but no such limit exists for downloads from the internet.
Wifi needs the password re-entered after every reboot and the last hotspot is saved with a number appended. (means the device will save hotspot 1, hotspot 2, hotspot 3...)
I am using the dual-sim phone, could this be a reason for my no sim detected message in cellular settings? (the UT menu under the not useable Cellular data switch lists me both sim however)
Camera just loads but never starts and the GPS switch is not useable.
In fact both the GPS and the Cellular data switch have a black background where the flight mode switch is grey when deactivated and green when active.
The SenSorstatus APP from the store seems to get absolutely no data from any sensor (compass, gyroscope etc. - in that respect TUX Racer will also not have any steering)
Is it possible that I have installed one of the images or even UT on the wrong partition or something? Maybe mixed the Boot or System destination? I am still trying to find out how to actually read out which data I flashed exactly where and it is curious that you and I both had Android 8 and used the same installer etc and now have two devices with such different functionality.
Cheers!

Hi guys, I am following Lakotaubp s request on https://forums.ubports.com/topic/4147/sony-xperia-x-performance-dora-f8131-f8132/36 to post here... It seems I am the first, so I am not sure if I am doing it the right way
First of all, thank you so much for being here (as I understand, especially to Andreas-Pokorny) and giving such amazing advice to allow me to enable this project that I had had my heart on since they announced the Edge - and left us hanging...

I had a tough day yesterday following all the advice on several forums, but mainly here. I am not sure if it would help to explain my issues - one main problem was that my fastboot would not take any commands despite having found the device using

fastboot devices

in the folder with all my tools

from: https://forum.xda-developers.com/t/q-cant-unlock-bootloader-software-says-i-can.2558539/ I finally found that the command:

fastboot -i 0x0ffce oem unlock 0x(my key here)

would allow me to fully unlock my bootloader (after having obtained the key from sony as described in previous posts. (I am not sure if you guys did not face this issue, or have a different reason not to mention this - maybe it is also just my inexperience in flashing devices that made me struggle so much, as no one on google seemed to explain this anywhere...)

Now I have a beautifully working system after initial installation issues with bootscreen crashes with twerp being the solution (despite error message) also as you guys have beautifully explained

Now my issue and and a question
UT works like a charm on my device, it is fast and everything. Browser works, appstore works, but needs several attempts for larger apps.
I was able to transfer an image via USB cable from my Ubuntu 20 PC, but not a folder with 12 mp3. The copy process then froze.
The sad part is: I can not turn on my location. and the Camera only starts to load, but never shows, and it only states No Sim detected in the according menu.
This seems very similar to the problems jlabon seemed to face a few days ago, but apparently updates fixed it for him? (can I to do something to update to build 115?)

Is there a simple solution maybe?
I followed the advice to use the 16.04/arm64/hybris/devel channel, is this still the most recent?
I used SW_binaries_for_Xperia_AOSP_N_MR1_5.7_r1_v08_tone.img (Android 7.1 despite android 8.0 being available on the sony website)

As I felt I nearly bricket my device yesterday, will a new installation be as tough as then? Or will it be only the UBports Installer? How do I find out if I used the android 8 SW_binary? as I had also downloaded it after several failed attempts?
Thank you for reading through all this. I still feel brain drained from yesterdays deep dive odyssey, and this may be less organized than I would like