#PeerTube is a free open alternative to YouTube:
It's federated through ActivityPub, so you can follow PeerTube channels on Fediverse sites like Mastodon etc.
It uses peer-to-peer technology so even viral videos won't bring an instance down. The more people watch, the more bandwidth they contribute.
There are several apps:
-#Mastalab ( @tom79 ), also works with Mastodon
-#PeerTubePlayer, on #Fdroid and Play