Syncthing worked when I installed it, but it was extremely slow. The FAQ told me to go through Firewall Setup which took some time.
In the end, I realize all I needed to know was to click on each Remote Device, choose Edit, then Advanced. Under Addresses replace the default “dynamic” with something like: tcp://192.168.1.xxx:22000
I know this won’t solve everyone’s speed issues, and this is probably very obvious to many, but I hope this might help someone else struggling with Slow Sync.