SOLVED: "Playback failed due to a fatal player error." (Only in Firefox)

[altair]

Did you switch to VAAPI?  You showed the screenshot of you switching, but the log is still saying you're using QSV?

I noticed that the output of the transcode is 4K.  I'm wondering if that iGPU just doesn't support transcoding to that resolution.  In Firefox, go to the Settings > Playback menu (not the one in dashboard) and set the max transcode resolution to 1080p.

Ah yes sorry my bad, that was the old paste, here is the with VAAPI : https://pastebin.com/EnYYNrY4

And here is the log with max transcoding set to 1080p on firefox: https://pastebin.com/uzXx6v7B and apparently as you can see it plays on firefox although its quite choppy if you try to move around... 
The thing is on chromium browsers i can play it on 4k with no problem at all smooth as hell and even when moving around in the movie the playback is almost instant its almost as fast as playing local so the iGPU is probably capable of it since it works on edge.
Here is an image of player info from edge:


And here is one from firefox with capped transcoding at 1080p:

Hope these tell you something more.

Also here is the log with setting max transcoding to 1080p on my android device(xiaomi mi 10): https://pastebin.com/iWdjLGqg still isn't working there... even tried 360p to no avail. So no screenshot from there i still get the "Playback failed due to fatal player error"