@yoorick i have the same problem

Opera ignores at the firts start german umlauts from my keyboard like ö ä ü ß. But when i restart opera several times (3-4x) then it works. First only ä later ä and ö and later all umlauts. Version 58.0.3135.53 OS=Ubuntu 16.04. In Texteditors like gEdit i don't have this problem
Rainer