Full Disclosure: I work here.
Then my NAS died very prematurely, rather than buy another proprietary piece of hardware from Synology I muddled through setting up DSM in VirtualBox on a more powerful machine with xpenology. Using their operating system in a virtual machine lets you use their mobile apps too, about the only thing you can't do is use their QuickConnect service but there are other dynamic-dns services you can use in its place.
https://xpenology.com/forum/topic/13834-virtualbox-dsm-62-ds...
rsync is incredible efficient and reliable. I use Nextcloud for some things. But it is just too slow for large data (Gigabytes and tens of thousands of files). Especially it they change frequently. HTTP and webdav is slow and the clients are not reliable. Last week I tried to transfer 20000 photos (for Mapillary) from a phone using Nextcloud. It took forever and the Nextcloud app crashed after a few hundred photos. Rsync (syncopoli on the phone) worked like a charm and did the job in no time.
Plus it is just so convenient using SSH because you can easily make tunnels and still have end-to-end encryption.
I have an instance running at home (reachable only via VPN) that simultaneously syncs the files via Syncthing, and the combination of the two is surprisingly effective.
