Thank you for the welcome.
My post is not about "Flash not working". I dont have Flash installed and I dont want to either,

Its about videos/streams that work without Flash in other browsers (in my example Firefox) but not in Opera.

edit:
It might be something about h.264 since on the HTML5-Test-Site in Opera that codec is not working but in Firefox it is.
I do however have "libx264" installed.
I found one suggestion to install "opera-ffmpeg-codecs".
Before I do that, is there a way to make Opera use the codec from "libx264"?

Just a small correction, Chat works in Firefox after all.

Hello,
Twitch videos dont work with my Opera saying "No supported video backend available; Flash is not installed".
And its true, I dont have flash installed.
Twitch should work with html5 though and it does so in Firefox.
What seems weired is that in Opera I can see the Twitch-Chat (which sould be html5, no?) but not in Firefox.
Any idea what I could try (except installing Flash)?

I tried to google a solution but could find anything the worked.
Youtube for example works fine.

Im running Manjaro Linux (x86_64; GNOME) and Opera 43.0.2442.1144