I assume your settings->Display->Advanced->Rotation settings looks similar to this:
If it does, then you might try to install an app which is able to check your sensors (especially rotation sensor here…).
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Yes, it does look like that… At which apps do you think?
Well, I think there are loads of them.
Maybe an interesting one might be “phyphox”. You can find it also in F-Droid. Besides Gyroscope test you find a lot of other nice sensor features there… 
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Any ideas?Thanks for the link, @volker, I haven’t found this. Glad you searched it up for me! 
So @stanzi, if I read right in this topic mentioned above and this one: Installing from scratch is not scratchy enough, you formatted your phone, installed UBports, then formatted again and installed LOS? Afterwards all the sensors worked again? Sounds not very logical, but if it works…
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I also tried to flash both LOS and OpenOS multiple times before, along with formatting the entire phone (except TWRP probably), reflashing TWRP multiple times, flashing the drivers via the modem file, but nothing worked.
It doesn’t sound logical to me either, but it worked, so I didn’t question it 
Well… I give it a shot.
Did you install LOS new or do you think a TWRP recovery IMG will do the job, too? I guess I’ll try that, so I don’t need to set up everything anew…
Man, so I spent the whole afternoon with that. I’ve managed to install UBports with their buggy installer (I’d love to type some lines in the terminal… 
). I tested two different kinds of sensor apps, screen was not rotating in UBPorts and no sensors working. Well, I thought you had it only afterwards, so I tried to install /e/ again… I can’t access TWRP now, I can only start it with adb. I have always the UBports logo in the recovery mode. /e/ is installed successfully, but no sensors work…
Any hints?
Just to avoid confusion:
TWRP can be booted with fastboot, see twrpwoflashing. Fastboot is not ADB.
UBports installs its own recovery. If you want to have TWRP back in recovery mode, you just have to install TWRP again … Fairphone 2.
Because the installer was so buggy, they introduced manual installation instructions a while back. I wanted to link to them now, but it seems they are gone.
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Hello @AnotherElk,
thanks for your answer.
In fact, I’d like to have TWRP back again and accessible by the hardware-buttons. So I installed TWRP again, but it doesn’t work… Fastboot works, I can even install /e/ with it (which works, but not the sensors). But adb seems not to connect… For adb reconnect it gives no devices/emulators found back… And I am still with the UBports recovery…
How can I uninstall that?
What did you do exactly to install it?
Ah, I think I see a possible problem.
The “Fastboot Install Method (No Root Required)” begins with the device booted and with Android running.
Scrap that.
Forget the “adb reboot bootloader” part and just start or reboot the phone while keeping the Volume - button pressed to boot the phone into Fastboot mode (aka bootloader).
Then you can continue at “You should now be in fastboot mode” 
.
ADB works when Android is running and USB debugging is enabled in the settings … and it works when TWRP is running, but only with a subset of the possible commands … and recovery programs tend to support ADB Sideload to install stuff, but you have to switch them into receiving mode for ADB Sideload first, so the computer can push the install file to them.
By successfully installing TWRP, or any other recovery program.
I don’t recommend formatting the recovery partition because it simply is not necessary … and you would still have to install a recovery program if you want to have a working recovery mode.
fastboot flash recovery twrp-3.3.1-1-FP2.img
That should work, isn’t it? 
What’s the result of the command? Some error message?
<waiting for any device>
then nothing…
Fastboot is not recognizing your phone.
Is the phone connected to the computer and booted in fastboot mode (only the Fairphone logo is displayed, with current modem files additionally the blue LED would be blinking and at the start the phone would have vibrated a few times)?
I have the Fairphone-Logo “powered by Ubuntu”, but no LED blinking (I never had that, I think).
Exactly!
sudo
doesn’t do it either…
Ok, I just installed UBports on a Fairphone 2 (Oh, the installer works, when did that happen ?).
I rebooted into fastboot mode … it’s as you say, UBports changed the splash screen … but that doesn’t matter.
fastboot devices found my phone.
And fastboot flash recovery twrp-3.3.1-1-FP2.img successfully flashed TWRP to the phone. Looks like this:
>fastboot flash recovery twrp-3.3.1-1-FP2.img
Sending 'recovery' (10384 KB) OKAY [ 0.333s]
Writing 'recovery' OKAY [ 0.117s]
Finished. Total time: 0.508s
And now I have TWRP when I boot into recovery.
Sorry, I don’t see what’s wrong on your side. I’m using Windows, though.
Maybe try a different cable?
Or the official platform tools (could be newer than what your Linux has)?
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