https://symless.com/synergy/downloads
Use libcurl workaround (since we Ubuntu apps need libcurl4, but Syergy needs libcurl3)
sudo apt --fix-broken install
sudo apt remove libcurl4
Get PPA: https://launchpad.net/~xapienz/+archive/ubuntu/curl34
sudo dpkg -i ./synergy_1.9.1.stable_b327+2a0225c1_amd64.deb
synergy