Dear all,
thanks again for your several comments: Indeed the only thing not working before all started were some disfunct channels / services, the box with its (old) image was working. I simply should have kept the image and only updated it with fresh channel lists. But well...
Now for the last commenst from rantanplan: yes, I also retried the whole procedure with the latest 8.x image, and the results are perfectly the same. I can only scan and tune into a very limited list of channels. The choice of transponder seems to be random: today I got a bunch of crappy channels that I had never heard of. And none of the maninstream ones (ARD HD or SD, ZDF HD or SD,...)
I just got myself a replacement et9x00 model and it seems to work well, at least better. So I am again suspecting a hardware defect, somehow mysteriously triggered... maybe the power supply does no longer deliver all the different needed voltages. I remember having had to replace one of its elkos (Elektrolytkondensator) some years ago.
So don't bother, let me try to find out now how to set up the replacement , without breaking everything again.
[I could also try to switch the power supplies - not sure if I will]
Tx
THN