Cam Link can directly send video to various applications, including:
Game Capture HD
Cam Link uses the UVC protocol (USB Video Device Class):
Products that use the UVC protocol should work in any application that support webcams.
In recent versions of macOS, Elgato Cam Link will need to be given Permission to use your Mac's Camera and Microphone. You can do that via the Security (or Security & Privacy) section of the System Preferences.
Elgato has not tested Cam Link with every possible application, but Cam Link definitely supports UVC and should work as a webcam in your favorite applications.