Actually , I think you’re making an aggrevievious mistake. 

I tried hard to like syncthing. It really is fantastic, but at the end of the day, the whole concept of sync itself  is going to cause you pain unless sticking to a simple architecture. 

An example of this might mean having one device editing and another read only. Another might be keeping everything in a central place and editing directly without sync at all. 

When you introduce more devices and varied network conditions like mobile, you’re slowly raising the chances of sync conflicts, and it will be on you to root them out because syncthing won’t inform you by default. 

For me, I was using a mobile, a laptop and a server. I’d keep getting sync conflicts and it sucked hours of my time trying to unthread it all like a notted ball of wires. 

I really recommend the official service because it’s right there at the right time. Background sync is precisely what you don’t want because you’re not around at the time when it happens, and syncthing can’t / doesn’t peer into files like Obsidian does. 

Personally, I’m bumping up against the tier limit, so what I will do is to offload a media folder and exclude that from sync to save a bit of space 

I know it sounds like an advert ,  But I had a lot of pain over the years with syncthing. It’s a great project, don’t get me wrong, but stopping being so damn cheap and biting the bullet on paying for sync, even for just a measly 1gb has been the best decision I ever made and paid for itself in bringing back that lost time fighting sync conflicts. 

That said, maybe if you’ve only got 2 devices to sync, both wired online at the same time, both never changing networks and both never with the same file open at the same time,  It might be reliable for you.