I don't feel like the way we're doing it today is the best approach, but I'll share what we do haha
I run all my community events through Luma (both in-person and virtual) while other teams mostly use landing pages/Marketo sign up forms. My virtual events are through Zoom and I host them on our community account while other marketing webinars are run through a different one. I do occasionally share events from other departments in the community. I'll usually add them as external events on the Luma calendar, include them in my weekly roundup post, and occasionally I'll create dedicated tightknit events to share in our events channel.
In terms of event promotion, email is a big driver for us. I usually email our broader user base and not just our community since most of the content is product enablement/use case sharing kind of stuff. It helps bring awareness to the community as well and is a big driver of new members.
The thing that customers probably find confusing is that there's a community events page, a regular Amplitude website events page, and then our Academy also runs evergreen live sessions around using the product. I think it would make a lot of sense for these to be consolidated so it's easier for customers to understand everything going on, but we run all of these through different platforms so it's not that way. I also get that it could be overwhelming and hard to parse through so you'd need good filtering