I created this quick little wiki page on possible integration ideas in regards to Hubzilla (the fediverse) and Nextcloud. Feel free to edit it and add additional thoughts or input. I've tried to include links to related discussions happening on the Nextcloud help forums and Github.
Some items of interest that may be unrealistic, but fun:
Zot protocol support in Nextcloud for nomadic identities
Federating calendars and contacts
Mounting external webdav storage into Hubzilla --
mentioned here on Hubzilla support forumNextcloud adding federated nomadic identities
Nextcloud file, activites and comment sharing via ActivityPub to fediverse
@
Björn Schießle and @
Andrew Manning might have some goods suggestions. Hope you don't mind the mention.