npub1aem2tstsjh9yxetrn9732y3x44dj3sw7rtjesv09vlmzxvtryk5s29r94a (npub1aemβ¦r94a) in the URL bar, type `about:config`
it'll give you a search bar, type (or paste) `network.http.http3.enabled`
you click on the result and see if it says `true`
if it says `false` double click it so that it changes to `true`
try youtube and see if it works