No info on that online...
No real info, but in order to debug a prefPane now, you need to connect to:
except you'll have to disable SIP to do so. In the past you could debug while running in a self-signed copy of System Preferences, but even if you self-sign legacyLoader, there is no way to tell System Preferences to use your self-signed copy.
I wish they would fix this. I am delaying the purchase of a 16" McBook Pro because I would be forced to run Catalina and have no way to debug without disabling SIP system-wide.