Huh? Nextcloud has mobile and desktop clients, including end-to-end encryption, lots of features around sharing files (both publicly and inside organizations),...
They don't have end-to-end encryption for their contacts, calendars, tasks and notes, which is what EteSync does...
Anyhow, I changed the title.
Regarding the comment you were replying to: the NextCloud clients, for all I know, don't actually sync with your filesystem, they just have a UI for accessing your files.
Also, their files support is pretty poor, no? Only a web view, no "dropbox"-like clients.
Anyhow, we plan on adding file support soon too. :)
Edit: I updated the title a bit. I hope it makes more sense.