> It's not so bad on Linux or OS X, but that's quite a bit of extra work on Windows.
Nowadays, we have wireguard, so you can create a secure little network to run this sort of thing over much more easily.
Running tailscale (https://tailscale.com/) on each machine you're using, and then using their tailscale private ips with synergy, should be both secure and work painlessly across those three platforms
If you're on the same layer 2 broadcast network segment (typically some machines in a home office plugged into the same dumb switch, or all on the same VLAN), the time/effort to do this with ssh is a lot less than using wireguard to talk between two machines that are literally plugged into the same switch.
Since the typical use case for barrier is to have something like two desktop PCs, each outputting to two displays but with no mice or keyboards, and one laptop in the center, where you want to use your laptop's keyboard and trackpad to run everything.
The comment above was about how running ssh forwarding correctly on windows is involved and has awful UX, which is true in my experience too.
Tailscale has much better UX, so it solves that problem.
In addition, wireguard is just as simple to setup as ssh (again in my experience), can operate over local LAN too, and some people have found it to have better performance than ssh forwarding (such as https://news.ycombinator.com/item?id=21162273).
Nowadays, we have wireguard, so you can create a secure little network to run this sort of thing over much more easily.
Running tailscale (https://tailscale.com/) on each machine you're using, and then using their tailscale private ips with synergy, should be both secure and work painlessly across those three platforms