Oh forgot to add that the last case that you mentioned, where multiple users sharing a PC, and keeping the folder in sync with all, is not straightforward. This needs another always-on (server like) device.

At least in Windows each user gets a different Syncthing ID. So if you sync the file with an always-on device, the other user can get the update when they come online from that.

Here one crucial element that needs to be highlighted is Syncthing is decentralised by design. I mean it is different from a server-client way of thinking. It is very much like how git stores content, if you are familiar with it.

For example, let us say I have 5 devices and there is a folder I want in all my devices kept in sync. Since there is no server, to propagate updates made in one device (let us call it Source Device) to other devices, it has to happen either directly, or indirectly. Here I'm assuming all 5 devices are configured to communicate with each other directly.

Whenever one of the other 4 devices (Device 1) becomes 'online' at the same time as of Source Device, the sync will happen. This is the direct way. The indirect one is, let us say after the sync happened between Source Device and Device 1, the Source Device goes 'offline', but the Device 1 continues to be 'online', now if Device 2 comes online, the change will be propagated from Device 1 to Device 2.

Note that the assumption, one device configired with all other devices is not the case, propagation of change has to take a path that similar to indirect way, even if all the devices are simultaneously online.

This configuration, where each device is configured to communicate with all other, is a pain to maintain, since Syncthing is not designed like a publish-subscribe model. What people usually do is, an always-on device (usually a server) is used as one of the devices that need to be kept in sync. Again, this is not a client server model, but each device is a 'node', and the always-on device is also just another node.

As you already experienced, it is very easy to get sync conflicts, if a folder is shared between multiple users, because of this decentralised design. In my opinion Syncthing works best for a single user. My use cases are, syncing my notes between pc and mobile, sync files scanned with the mobile to my pc, etc.

If your case is more focused on multiple users, WebDAV server can be an option. But again it's not straight forward and may not cover all use cases. Depending on what you are trying to achieve, a tool more suitable might be available. For example, if the aim is collaborative development there is Iroh (Still in early stages of development)

I hope this helps.