It would be good, Syncthing could synchronising files across folders attached to same physical device, local folders located on local drives.
It’s not a usecase we support or plan on supporting.
I read and understood the thread, it is also for you an interesting thing, but not so easy to implement and not necessarily in the concept focus.
I feel similar to the writers in the thread. I have about 10 of 62 peers in total which I synchronize locally and would like to use one tool and not several.
That’s not a great justification for duplicating the functionality of another tool though. Our efforts are better spent making Syncthing better at the things other tools are not good at. The alternative is making Syncthing a great archiving solution, antivirus scanner, document editor, web server, and whatnot. It’s not a road I’m interested in going down. (Those are not made up strawmen by the way, except for maybe the virus scanner. The other ones have all been suggested as things we should do, one way or the other.)
I well understand your point of view.
In the above thread I read from you how about the possibility to solve this with several instances. I’ve already tested something like this on a Synology by running the package installation and a Docker installation in parallel. However, I have the problem with the Docker installation that all files are stored almost twice, in the Docker container and parallel in the path of the file system that I link in the container. Otherwise I could easily get the 10 peers e.g. manage with a Docker installation. But then double data storage?
This is all a good hint that you are using the wrong tool.
In fact with that test condition you are right. In productive condition I use for local sharing Resilio. However, I have the feeling that it is better to build up an alternative in the long term.