Elgato's HD60S device does not show up as a webcam on in Mac apps. (It does not have UVC support.) So unfortunately it is not compatible with Ecamm without additional software.
Using OBS Link
It's possible to enable the HD60S using an app called OBS Link. Steps to set this up can be found on Elgato's website.
Note that the article refers to using OBS Studio. This isn't required to use the OBSLink software.
Once installed, you'll see a new camera in Ecamm called OBS Link.
HD60S vs. HD60S+
The newer product, the Elgato HD60S+, works fine without additional software.
See this Elgato Support Article for details on the differences between the HD60S and HD60S+.