Форум поддержки Firefox

So the problem is that Firefox doesn't play any HTML5 content. Weirdly except for Youtube. Youtube works just fine. But every other Website shows errors. Even songsterr.com. I'm using latest Firefox 76.0.1 on a recent Ubuntu 20. 04 LTS installation. Usual troubleshooting like updates doesnt work because "sudo apt-get upgrade" doesn't find any updates. I tried the same websites in the latest version of Chromium and they work perfectly fine. I couldn't find a mistake in the firefox settings or something so I'm confused. Disabling Plugins didn't change anything and turning of tracking protection didn't either. What is the Problem here and how can I solve it?

Recently, when a popup window appears, the toolbar doesn't have buttons for any of my addons.

In about:config, I'd intentionally set dom.disable_window_open_feature.toolbar to true (following the solution provided in: question 1206512).

Previously, this was successful in ensuring that popup windows got the full toolbar, but now it has stopped working.

I'm not sure exactly which release this started with.

Steps to reproduce:

1) Set dom.disable_window_open_feature.toolbar to true.

2) Visit https://jeffersonscher.com/res/popit.html and follow the third link.

3) The window that pops up has no toolbar icons for the installed extensions.