Source?
I checked for that, see this example video (NSFW) In Lemma I don‘t have sound but if I open it in browser it does.
How is the video requested? I have seen some lemmy instances just append "-mobile.mp4" to the normal link and that usually leads to no sound (for unknown reasons). The only way I know to get the full video is through their API, which needs a token request first. I‘ve dealt with it for a user script I made
In Germany you can use eis.de but they don’t deliver outside of Germany and their website appears to be only in German