First-run wizard breaks and renders NextCloud unusable when video autoplay is disabled

[deviant]

Steps to reproduce

1. Ensure that audio/video autoplay are disabled
2. Open NextCloud

Expected behaviour

NextCloud can be used

Actual behaviour

A blank white rectangle on a dark transparent background appears, blocking out the UI. It is impossible to dismiss this, and NextCloud cannot be used normally any more. Turning on audio/video (not sure which of these is important, probably video?) autoplay and refreshing displays the first-run wizard and allows me to click through and close it. I would attach a screenshot, except I don't know how to trigger the first-run wizard again.

This isn't a problem with how my browser is configured; NextCloud should not become bricked when videos cannot be autoplayed just because it wants to display a fancy animation to new users (or users who have just upgraded NextCloud, as in my case). It should fall back gracefully and display a static graphic. For new users, this is obviously a pretty terrible user experience.

Server configuration

N/A

Client configuration

Browser: Firefox 129.0.1
Operating system: N/A

Logs

N/A

Nextcloud log (data/owncloud.log)

N/A

Browser log

Don't know how to retrigger the first-run wizard, so can't get these.

[szaimen]

Btw, @susnux any idea how to resolve this?