> it isnt an advert, but some twitch-related thing i have never seen that says stuff like "preparing the stream" and "an intern stepped on a wire while your stream was setting up"

Twitch pre-roll played an ad for me on mobile in the web browser. Maybe you have an ad blocker in the browser you are using so it’s not loading the ads themselves and instead falling back to some twitch-related message?

Also I only got preroll on the first one not on the second or third. Maybe if you have an ad blocker it keeps trying prerolls more often?