Best I can tell mid this year the MS Edge user interface removed the option to manage protocol handlers. We are incorporating them into a project we are running and mid project saw the UI option disappear. We've confirmed the protocol handlers for Edge on Windows still work in the latest version (as of October) if you configure them via the Windows registry and/or group policy. I assume that on Mac the documented method will still work there too.
Nothing at the above documentation suggests the policy is depreciated, so should be OK to use it if you can get around not having Edge support the settings via the UI.
edge://policy showing the recognised and applied policy on MS Edge v141.0.3537.57