OK, can you please give the output of:
flatpak run --command=curl org.mozilla.firefox -D - -s http://www.google.at | head -1
and
flatpak run --command=curl org.mozilla.firefox -D - -s http://212.33.36.186 | head -1
if my current assumptions are correct, the first one shouldn’t output anything and the later one a HTTP/1.1 302 Found. Is that correct? If yes, please also give me the output of:
ls -la /etc/resolv.conf; cat /etc/resolv.conf