Valve released a new chat a few months ago:
https://steamcommunity.com/updates/chatupdate

It's new and all web-based now.

It has new group chat settings, looks more like Discord/slack now.
For example:
-Group chats can now have multiple text channels and voice channels.
-Steam media upload (pictures) and embedding of content.

Any idea if you will add support for this new chat? Or if it's even possible?

Because your steam implementation gets used by matterbridge and that is broken for now (42wim/matterbridge#457 (comment))