The Fediverse has its own video platform called @peertube.

You can follow PeerTube accounts from Mastodon, for example try following @craftykat

You can watch and interact with the videos entirely within Mastodon, or on PeerTube itself.

Here's an example of a PeerTube server:

➡️ https://fedi.video

If you see an account you like, you can copy and paste its account address into Mastodon to follow it there. When new videos are published, they will appear in your Mastodon timeline.