Syncthing works brilliantly! The web UI is excellent, warns you when you're about to do something ill-advised, and stuff like QR codes makes adding clients and folders fairly easy. The separation between folders and devices is handled well. You can easily have half a dozen shared folders between several computers with any mix-and-match combination including which one is 'authoritative' and so on.

I used to use it on Android to keep my 'camera roll' synced to my desktop. I preferred setting the ignore file to exclude android's thumbnails directory, but otherwise it worked great. I'd take a photo with my phone and almost before I could open the shortcut on the desktop, boom, the photo was there, since the android client detects changes in the filesystem.

I also used it to sync my password database, and a cross-platform notebook app's database. Worked flawlessly for all of them.

Ditto for a folder shared between my MacOS laptop and Windows desktop.

Lots of controls, especially in the forked android client. Don't want the sync client to run on any network other than your home network? Done. Don't want your syncthing clients to try and do NAT transversal / discovery outside whatever network it's on? No problem.

The biggest bummer is that there's no iOS client. Had to switch to Nextcloud, which so far has been working OK, but the number of people that have problems with the iOS client is quite high (problems such as syncs being so slow it takes days to sync a camera roll), and it's generally sluggish and doesn't work in the background (yes, I know, Apple's fault.) However, Nextcloud does allow me to sync contacts and calendars (I think. I haven't tried to set it up yet.)

One warning: Sycnthing really does not like it when you delete the dotfile folder inside the shared folder(s). Don't do that :)

I tried Syncthing, then I tried Nextcloud, and for the goal of just syncing camera roll and backing up my password manager, they were both a bit of a hassle.

Now I use Minio with FolderSync (Android App, I use the paid one, but the free is perfectly capable) to backup my camera roll and I wrote a very simply WebDAV server in Go to backup my (Android) password manager DB which only supports WebDAV, I sit NGINX in front of them both to terminate TLS and to handle basic auth for the WebDAV server, though I could easily implement basic auth in that too (again, my password manager only supports basic auth).

If someone can suggest a better password manager for Android with a good UI, good integration (e.g. auto-fill), has a Linux desktop app and can backup to WebDAV or Minio I'd jump in a heartbeat.

I considered Bitwarden, but I don't want to run the Mono/Windows server container, and I don't want to rely on the Rust port which is behind in features and is susceptible to the upstream breaking APIs.

"The server project is written in C# using .NET Core with ASP.NET Core." https://github.com/bitwarden/server

Seems like alternative DB providers is in alpha stage right now.

Mono and netcore is not the same, netcore is one of the more wonderful things I've worked with if I'm to be completely honest. Then again, I also kinda like PowerShell