OwnCast is a Fediverse livestreaming platform with built in chat, and is sort of a Fediverse alternative to Twitch.
You can follow the project itself at @owncast and find out more on the website at https://owncast.online
You can follow OwnCast accounts from Mastodon etc and they will let you know in your feed when they go live.
Some good accounts to follow include (in no particular order):
@live - Live DJ sets, soulful house music
@jnktn_tv - Live DJ shows on Saturdays, lots of different music styles
@Hamish - Live streaming retro games, electronics projects, programming etc
@rstv - 24 hour streaming of weird retro films and TV
@hatnix - Linux gaming streams, usually in English but sometimes in German
@fedi - Monthly show by the Small Technology Foundation, promoting small scale privacy-friendly internet projects
@ozoned - Live streams about Linux and gaming