Your html looks wrong to me in your second example.
The type should be closed with " not continued with ; Codecs should also use" "
I don't think the Codecs bit is needed though. Having the Type correct should be enough.
<video controls preload="none"> <source src="FooBar.mp4" type="video/webm"> </video>
Edit: Also presumably your files are definitely AV1? Double check that. I think you can also drag and drop video into Firefox to see if they will play.
Edit2: Also on searching I've seen someone say you may need to use the video tag itself for mkv:
<video controls preload="none" src="FooBar.mkv"> </video>
It's one of the solutions lower down on this stack post, but you'd need to test that. https://stackoverflow.com/questions/21192713/how-to-playback-mkv-video-in-web-browser
As a side, it's very frustrating to see how many people wrote code on that page that just works on Chrome. So much for Web standards!
Democrats need to play this carefully.
"protect our undocumented immigrants" plays into the MAGA playbook that the dems are weak on immigration issues.
I don't know what the right play is though. All left leaning parties find it hard to communicate clearly on immigration issues.
But this kind of headline at a glance makes it look like the governor of illinois is in favour of illegal immigration?
Its difficult topic to communicate clearly on when you have the right behaving hysterically about the topic and conflating terms like "undocumented" with "illegal" in people's minds.