Concerning problems with internet access from Andoid apps:
On my 10 III I disabled ip v6 for mobile connections because of problems roaming in Poland and Austria.
I kept that setting and just set it to ip v6 only for a test:
Fennec can access the internet with settings to dual or ip and fails with ip v6.
A broken ip v6 stack might explain a lot of problems with certain providers, roaming etc.