[SOLVED] I have created an issue on github almost a month ago...

[AndrzejL]

Hi Conor,

Quick update - I have found the root cause and it's fixed.

The issue was NOT a bug in jellyfin-web after all. It was a Content Security
Policy header in my nginx reverse proxy configuration blocking blob: URLs.

jellyfin-web 10.11.x switched Chromium browsers from native HLS to hls.js
(PR #7274). hls.js uses blob: URLs via Media Source Extensions (MSE). My nginx
CSP header only had:

default-src 'self' https: data: 'unsafe-inline' 'unsafe-eval'

Adding blob: fixed it immediately:

default-src 'self' https: data: blob: 'unsafe-inline' 'unsafe-eval'

In 10.10.7 Edge used native HLS which doesn't need blob: URLs - so it worked
fine behind the same nginx config. The 10.11.x change exposed the gap.

Regarding Matrix/Discord - I appreciate the suggestion but I prefer keeping
technical discussions on searchable, archivable platforms. I am a bit of a boomer...
Chat platforms don't preserve knowledge well - if a server goes away, all that
context disappears with it. Forums and GitHub remain searchable and benefit the wider community
long-term. I'll be posting the full solution back to the GitHub issue.

Thanks for pointing me in the right direction with the bot analysis - it helped
narrow down the hls.js angle which led me to the CSP blocker.

Cheers,

Andrzej