So, Nextcloud is not just a "backup". This is for a complete teamwork app. You can share files, sync your contacts and calendar from the phone (see DavX5), organize meetings, yku can use password manager, seeing and organizing photos, listen uploaded music, even track your bycicle tours on a map.

Nextcloud is written in PHP so it is fast (with memory caching it could be even faster - see: Redis).

There are apps for mobile not just Nextcloud client. See the app stores (if you have Android, see F-droid).

There are tons of plugins, addons, e.g. connect to weather service provider, Reddit or Twitter (oops: X) account etc.

💡💡💡BTW: #devs - a Nostr connector to Nextcloud should be developed too ⚡⚡⚡