For me the easiest solution was to tap on each field and then select the default option that the app suggests. This got things working, but i do not know how good - or private - these settings are.
In one of the other threads on this topic @tcecyk suggested 3 murena servers. I got those working by trial and error, but do not really know if what i did was in any way sensible either.
I think we, the users with problems, need to be better at not starting new threads, rather first checking thoroughly to see if anyone else has already asked a similar problem. Then people do not need to repeat the answers again and again and there will be a complete, definitive thread with all the info in one place.
Here are the settings i guessed at with the murena servers:
HTTPS: https://connectivity.murena.io
HTTP: http://connectivity.murena.io
Fallback 1: http://204.murena.io
Fallback 2: https://murena.io/generate_204
User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.32 Safari/537.36
If anyone can tell me if these are right or wrong i am sure the info might be useful to others too.