Scary … but nice ...
As if somebody @ UBPorts had read my first entry here, decided to quickly write 45 mb of code and change things drastically.

Well, a few hours later, there was the message on my mobile that 24.04 (r412) was there to download and install … which I did.
And now calling and sending text do actually work.

There are still some minor issues, but on the whole, I’d say I have a usable mobile now.

Things are obviously going to be better.
Thank you, UBPorts!

The only thing that really annoys me at the moment is that I am informed each time when I power up the device that the boot loader was still unlocked .. and that I'd better not store any sensitive data on it.

@Liam (and all others)
Problem here as well - with different result:
Tried to install UT on Fairphone 4 with Android 11.
Got identical screen: Installation stopped due to a problem.
I clicked ‘Try again’.
Installer then tried again, obviously trying to format (?)… which according to the installer didn’t go on. Still the installer didn’t crash. So I decided to wait. Took some time ...
Then suddenly everything seemed fine on the Fairphone. UT did actually boot – although the installer screen was still – unsuccessfully trying to move on – at work.
My problem is now that the installer somehow installed UT 24.04 (r411), although I thought I had instructed the installer to use 20.04 (stable).
And now I cannot use the phone for calls, and sms doesn’t work. There is only one network icon, the one with which I can connect to the internet.
Since I’d like to use a mobile to take sone calls, I am in trouble now.

I tried to install UT again (to possibly get the opportunity of going back to 20.04) – fail.
I tried to somehow install Android 13 to then later on try for a second time with UT – fail. Fastboot dces not appear to be able to detect my phone any longer .

So what to do?
Any idea how I can make fastboot work again?
Or might it be feasible to wait until there will be a new stable release of 24.04 … and hope that by then everything will work out?

I am not used to being in forums and I can hardly be called someone with much knowledge and understanding what actually happens, if you do this or that. I only try to follow instructions.
And: Should I better post this one as a new topic?
Complicated ...