I'm looking for something that can do chat, video calling with support for guess links and chats. I need it to work in the browser so I can send people a link to a chat session. Bonus if it has a simple mobile app and calendar integration.

Anyone know of something that isn't Nextcloud Chat?

Element Server Suite Community https://github.com/element-hq/ess-helm

I would suggest avoiding anything that is a "community" or "personal use only". If its not fully open its not worth it.