People have mentioned SyncThing and Seafile as straight backup options.
Another option one could consider is FolderSync[1]. It has a number of cloud back-ends it can interface with, but I use it to periodically SFTP to my home server to backup several areas in my phone, including photos, camera and app backups.
Two niceties for me it has:
* Two-way sync. I'll often clean up my camera roll on my PC, and that syncs back to the phone.
* Only attempts to connect to me home server if it is on my home wi-fi.
Putting my hat in this ring, too. I do a write-only sync of pictures from my phone to my NAS (upload new files and leave them on the phone - I prefer one way sync), and a mailbox-style sync of Signal backups (Signal can be configured to drop a backup file into a specified folder; I've configured FolderSync to upload whatever it finds there weekly and delete the backup locally). Finally, I do a two-way sync of my personal notes text file.
I don't have a good situation figured out for browsing unsorted uploaded photos, and I find that this is fine for my usage. I put a curated set of personal albums on a password protected personal site for friends and family. I enjoy the role of family chronicler.
My NAS is backed up via daily snapshot to a remote location.
I would also vote for FolderSync. I run seafile and nextcloud for other purposes, but have settled using FolderSync for phone --> NAS nightly backups and it is slick. I've been using Photoview to view backed up photos locally.
Finally. I thought I was crazy having to read through so many comments on here before someone mentioned just a simple SFTP to a backup server. FolderSync is the way to go.
Another option one could consider is FolderSync[1]. It has a number of cloud back-ends it can interface with, but I use it to periodically SFTP to my home server to backup several areas in my phone, including photos, camera and app backups.
Two niceties for me it has:
* Two-way sync. I'll often clean up my camera roll on my PC, and that syncs back to the phone.
* Only attempts to connect to me home server if it is on my home wi-fi.
[1] https://play.google.com/store/apps/details?id=dk.tacit.andro...