The Android version has an option ‘sync only on wifi’, which is of course to avoid synching over (often limited or expensive) phone data networks.
When that is enabled (btw, why only when that is enabled?) another selection becomes possible: ‘Restrict to certain wifi networks’.
That’s potentially useful, but in practice another option would be much more useful: “Avoid certain wifi networks” (I went through previous posts and couldn’t find a similar suggestion - sorry if I have overlooked anything.)
Use case: When using a mobile wifi router w/SIM card, to get wifi on the go. I’ve got one because my tablet doesn’t have a SIM card (the tablet automatically switches over to that one when I move out of range of other wifi networks). My wife’s one does have a SIM card in addition to wifi, but she doesn’t use that when travelling - then she (and I) will rent a wifi router in the destination country, and only access the net via the tablets’ built-in wifi. But we don’t want to sync over the mobile wifi router. Data limits, cost, etc.
On the other hand, as soon as we’re in range of ‘normal’ wifi networks we would want the sync to be backgrounding and active (in the home country as well as elsewhere). My tablet has a huge list of nets stored by now, and it’s continually expanding. It’s not practical to go through the list in Syncthing and tick off the new ones to add to the list of ‘Restrict to certain wifi networks’ all the time. It would be more logical and easier to tick off my mobile wifi router, and the occasional rented one now and then. A very short list to manage, as opposed to managing a list of ‘accepted’ networks.