This should be resolved by enabling audio over network using
This is what you need.
From the script of starting chromium-dockers
This will be cpu accelerated as there is no video hardware acc yet in rpi.
This have hww acc but only for x264 and x265 which was done recently.
Hard to say but try armbian while I don’t think they’re interested in getting widevine support with all these hacks that we do at Manjaro ARM project.
Btw the solution is available and used by many Manjaro ARM users idk why you’re not able to archieve the same results, maybe you’re not following the steps.