Cam Link 4K can directly send video to various applications, including but not limited to:
Elgato Game Capture HD
Elgato 4K Capture Utility
OBS Studio
Streamlabs OBS
Skype
QuickTime
XSplit
Cam Link 4K uses the UVC protocol (USB Video Device Class):
https://en.wikipedia.org/wiki/USB_video_device_class
Products that use the UVC protocol should work in any application that support webcams.
Elgato has not tested Cam Link 4K with every possible application, but Cam Link 4K definitely supports UVC and should work as a webcam in your favorite applications.
In recent versions of macOS, Elgato Cam Link 4K 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.
Please Note: The resolution that Cam Link 4K can send to an application depends on that application. For example, Game Capture HD has a limit of 1080p, while OBS can use higher resolution video.