An open and accessible way to distribute announcements should be the default: website, RSS, email newsletter. Anything else is a bonus on top.
And it doesn’t matter that much if you have a dedicated domain or if your page is part of a latger website. The important thing is that it can be accessed with a web browser and linked to.
(This appies to organizing that is supposed to be openly visible. If you’re doing covert action or organizing, very different strategies apply)
Heck, if you’re an organizer and don’t have the means to put up a website yourself, get in touch with some nerd. They’ll probably gladly put up a simple page on one of their 27 domains that they bought for giggles and never really use.
(Yes, I’m one of those nerds. Even though I have the domain buying habit a bit more under control 😅)