Hetzner $50+ servers have 1gbps uplink with unmetered BW.

That means the link can support less than 100 viewers at once on a video with 10 Mbps bitrate. Often a large portion of views comes in the first few days of a video being posted. You could probably handle the spike of views from a video that receives a couple of thousand views total (maybe even 10k), but more than that seems difficult.

Also, is Hetzner actually unmetered or do they claim they are with an asterisk?

I think it's actually asterisked. Iirc you get flagged over a certain amount of traffic, but I can't remember if they cut you off or just force you to pay more. I think it was several TB last time I looked.

There was limits before, but last two+ years it's unmetered without asterisk.

replying to Aerroon but it was too deep so replying here.

Is there a way to do it with some p2p à la popcorntime?

Then if there was a surge, the peers could absorb some of it.

Does peertube do that?

Peertube do exactly this. Webtorrent support it's main feature so you dont actually need powerful server for spikes in popularity.

Thanks I will take a look.