@Moem That worked! Wonderful! I am really pleased. Problem solved. The camera app simply reappeared after restarting the phone.
Steps (in the link):
1 open terminal app
2. Find the files:
sudo find /opt -iname *camera*
3. remove all files of that app that are listed
sudo rm -r PATH
4. reboot the device
Unfortunately, this had no effect on the (non-)existence of the camera app...
So ... No solution in sight. Well. Maybe I'll think of something later. I'll leave the thread unsolved and if anyone else has an idea - always welcome. I'll check in from time to time. As long as there's no camera in the cell phone.
@arubislander Oh yes, it's there. I've just checked.
@arubislander Mh... it looks like nothing is going to happen. It just appears again: phablet@ubuntu-phablet:~$
@arubislander I have the camera.ubports directory in the /usr/share/click/preinstalled/camera.ubports folder. But there was none in /opt/click.ubuntu.com/camera.ubports, where AppLee's folder ist located.
Im Verzeichnis /usr/share/click/preinstalled/camera.ubports
sudo cp -f -r camera.ubports /opt/click.ubuntu.com/camera.ubports
@AppLee The copying has now worked. Apparently I have to write “sudo” in front of everything. But that didn't help either.
Well, with the bug I also meant that the camera app somehow removed itself. It was simply no longer there after the restart. And now I can no longer install it. That's kind of annoying.
This morning I tried to see if a new installation (without ticking the ‘wipe userdata’ box) would be successful. Unfortunately, the camera app is still gone and can no longer be installed... I don't understand this anymore. What is the reason for this? Surely it must be possible to reinstall this app somehow? There must be some very strange bug behind it!
@Bolly Naturally. Otherwise there would be no point. 
That does not work. Nothing is copied. Not even via the terminal. The error message -r not specified appears. However, the path to the destination is correct.
@AppLee
lrwxrwxrwx 1 root root 50 Sept 21 1 1:12 camera.ubports -> /usr/share/click/preinstalled/camera.ubports/4.0.6
Before and after other app entries
Restarting the phone: the app is still gone, but the folder is back...
@arubislander I have tried this:
cd /opt/click.ubuntu.com/.click/users/@all
sudo rm camera.ubports
The camera.ubports folder was then also gone.
Unfortunately, this does not lead to the result either. Or the same as before...no camera app and no possibility to install it...
@AppLee I have tried changing the channels. Unfortunately, the camera app is still missing ... and cannot be installed. It almost looks like there are no more photos for me now... 
(I use a Fairphone 3+ with Ubuntu Touch 20.04 (OTA 5) The following problem: The camera app keeps crashing. A restart is normally sufficient.
This time, however, the camera app was gone afterwards. So I tried to reinstall it. Clicking on the ‘Install’ button leads to a progress bar (forwards and backwards) and then ... nothing. Instead of ‘Open’, ‘Install’ appears again.
Then I tried to delete the app completely and remove all traces (cache, config, local/share). The same result when installing. I then tried it via the open-store.io website with the current and previous versions. Nothing. Installing the packages via UT-Tweak-Tool shows that it is installed, but this is not true. The app is still missing.
Then I tried using the terminal and sudo apt-get install and as names lomiri-camera-app and camera-app. Package not found. Now I don't know what to do...
What can I do? I don't want to do without the camera. But I also don't want to reinstall my whole system (and lose all data..) - especially since I don't know if it would do anything.
Maybe someone here knows the location of the calendar from the Calender app? I like to make regular updates and can't find the file for the calendar. Who knows more?
(I mean this app: https://open-store.io/app/calendar.ubports)
devel worked for me too (Fairphone 3+ / i installed the update with the "stable-channel" in my phone updater). I'm afraid now to switch back to stable... In the updater on my phone, the update (titled with "Version 7") still exists, it starts to download and i paused it. So am i ever be possible to update my phone now to a stable version???
Of course I tried all the normal stuff. Put the phone outside - wait a long time. But it's no use. Also let the various apps with GPS try to locate me does nothing except the app finds nothing. Neither UNav, nor bing, nor google maps can find me. Also the clock-app can't find my location. The app sensorstatus thinks GPS is fine. Still, I can't use it.
