Not working with MediaWiki 1.39.1, the complete Wiki disappears and produces only a blank page.
Topic on Extension talk:EmbedVideo
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doesn't seem to be in super active development, yet half the world uses it... a bummer
Are you using Star Citizen Wiki's fork?
me? no
Original EmbedVideo isn't developed anymore since Gamepedia has been bought out by Fandom, and incorporated entirely into Fandom's platform. There's a fork by Star Citizen Wiki that keeps the extension maintained for everyone else - it's linked at the top of the page here, under GDPR-compliant fork.
Here is the page for the fork : Extension:EmbedVideo (fork). It requires a change in the code since there's no evt in the fork (the original parser function works with both named and unnamed variables).