Just stumbled upon this. There are many ways to share your Event and you can even create some Events anonymous. This is awesome for organizing protests or other events you want to publish but you dont want to be mentioned in them as creator.
It also can publish events into Mastodon.
there’s also Mobilizon https://joinmobilizon.org/en/
Yeah, but can you post events anonymous there? I tried it a couple of Years ago and i didnt See that Option. But maybe that changed since then.
Also it seems Less active for my country (germany). In my area there is a instance called https://bonn.jetzt/ which is quite active and is also posting on Mastodon.