Synergy used to be great, the original developers really knew what they were doing, but since then it's been taken over by a commercial developer that seems to have no interest in making a good product and far more interest in charging money for it and licensing - more bugs are introduced with every release, clipboard support is half-broken on Linux for years, the Synergy 2.0 release now causes my mouse to continuously leave my screen while gaming even when locked and random restarts of the service and jumping back to the middle of the screen are far too common. I have to revert back to a very specific version to make Synergy work acceptably and I'm reliant on it for my daily workflow.

Worst part is I actually paid them money for it hoping they'd have fixed it by now...

That's been my experience also. It's kind of surprising given that I was able to replicate 90% of the functionality (that I normally use) for a Raspberry Pi project using only netevent[1] and netcat. Obviously cross-platform and international support (+ handling edge cases) would complicate things, but even in the most basic scenarios, Synergy has been terribly unreliable for me lately.

[1] https://github.com/Blub/netevent