@pikario No need for "support", at least at this level. XEP-0503 is mostly redactionnal and explains how to combine other widely deployed and standard XEPs together.

You mix XEP-0060: Pubsub and XEP-0045: Chatrooms, you a pinch of XEP-0402: PEP Native Bookmarks (which is itself based on 0060) and boom, you have Spaces 🍰

Thats the true power of #XMPP 😎