Why does `apt install -f` REMOVE my package?

I'm trying to install Synergy 2.0.11, but I get a dependency issue:

Unpacking synergy (2.0.11.stable~b56+8c94f00f) ...
dpkg: dependency problems prevent configuration of synergy:
 synergy depends on libqt5core5a (>= 5.7.0); however:
  Version of libqt5core5a:amd64 on system is 5.5.1+dfsg-16ubuntu7.5.
 synergy depends on libqt5svg5 (>= 5.6.0~beta); however:
  Version of libqt5svg5:amd64 on system is 5.5.1-2build1.
 synergy depends on libssl1.1 (>= 1.1.0); however:
  Package libssl1.1 is not installed.
 synergy depends on libstdc++6 (>= 6); however:
  Version of libstdc++6:amd64 on system is 5.4.0-6ubuntu1~16.04.9.
 synergy depends on qml-module-qtquick-controls (>= 5.5.0); however:
  Package qml-module-qtquick-controls is not installed.
 synergy depends on qml-module-qtquick-dialogs (>= 5.5.0); however:
  Package qml-module-qtquick-dialogs is not installed.

In the past I've just ran sudo apt -f install and it picks up the dependencies. Now, however, it's sad and tells me:

The following packages will be REMOVED:
  synergy

Why is apt trying to remove my package, and how do I tell it to install the dependencies instead?