PI 5 | No H265

[venc]

Vivaldi on Raspberry Pi 5 not playing H265 videos (and probably more proprietary codecs)

Raspberry Pi 5 is capable of playing h265 videos by hardware. Chromium which is a default browser is working perfectly for this. And other media players as well when launched directly. But Vivaldi is not able to play h265 in any web page (e.g. Twitter/X and many other pages containing media), but it can usually play Youtube probably because it is using VP9 and other google formats.
I'm running Debian Bookwork 64bit for Raspberry Pi.
Is there any chance to get the proprietary codecs working or am I obliged to still use Chromium? So far no recipe to get it working was successfull for me.

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ModEdit: Title

[DoctorG]

@venc Does the inofficial script help? https://gist.github.com/ruario/19a28d98d29d34ec9b184c42e5f8bf29

[venc]

@DoctorG I'll test it till weekend. But the "flash" inside the name of the script tells me it's probably totally obsolete and it will only download old libraries and put it in vivaldi folder. I've downloaded widevine libraries manually right after installation. Maybe I did something wrong (permissions etc.] I'll try it once again.

[DoctorG]

@venc Had you read all the comments below script? Perhaps that can help.
I have no Pi5 to check.

[venc]

@DoctorG Of course... I'm currently away from my Pi 5. I will return there next weekend just to test it.

[venc]

@DoctorG Sorry for late reaction. H265/HEVC definitely not working on Chromium, Vivaldi and Firefox. But, there's a slight progress, because all versions of H264 are now working on Vivaldi and pages like Twitter/X and others are now capable of playing videos (and motion GIFs, which also didn't work), finally.
Widevine library as got by script in discussions is linked to chromium and vivaldi folders. The H265/HEVC videos are all playable in VLC when downloaded.

I've tested the codecs support here:
https://tools.woolyss.com/html5-audio-video-tester/