Why isn't it done yet?
Wayland is designed around a security philosophy that excludes software like Synergy by design. So, they need to make special exceptions to allow software like Synergy to work. We tired implementing Wayland support for Synergy many times, and it has cost us a lot of development time.
Because the Wayland API is constantly evolving and is still quite young, we have faced different security related challenges each time we tried to implement Wayland support.
However, there is hope! A Wayland library called libei has been developed which actually mentions Synergy a lot, hinting that this is the special exception we’ve been waiting for.
Please rest assured that Wayland support is very important to us, and we will continue trying to implement it.
Any workarounds?
Yes, most distros (e.g. Ubuntu) make it very easy to switch back to X for this exact reason; many programs do not fully support Wayland yet: How to switch back to X on Ubuntu
What is Wayland?
First, a bit of background: X.Org Server is the free and open-source implementation of the X Window System display server stewarded by the X.Org Foundation. Implementations of the client-side X Window System protocol exist in the form of X11 libraries, which serve as helpful APIs for communicating with the X server. We'll just say X from here...
There's a new Linux display manager that is set to replace X, which has been the de facto Linux desktop manager for as long as most people can remember!
Wayland is the new display protocol for Linux/Unix-like, set to replace X. Sadly, as of 2023, Wayland is incompatible with Synergy. Right now, many people have to choose: Synergy or Wayland. A lot of people are very unhappy about this.
Since Wayland is the way forward and X is being phased out, we are committed to doing everything we can to make Synergy work with Wayland. But, this depends on Wayland. Wayland needs to actually add support for apps like Synergy. The future does look promising, as Wayland community is now discussing Synergy support in the Wayland libei library. The Wayland libei library was created to add Emulated Input to Wayland, and is primarily aimed at the Wayland stack. The Wayland libei library even mentions Synergy nine times, which certainly sounds promising.