I’m not too familiar with nextcloud for now, but could it replace WhatsApp?
Like could you chat with people on the same instance and with people from other instances?
One of the downsides of WhatsApp is that it’s often used as a gallery to share images, but those are downloaded on the devices which leads to a full SD. It would be nice if you could talk to anyone on any instance and share (and have full control) images, files etc. Like XMPP but with unified sharing and acl system similar to upspin.io