I was able to build a simple Cloud OR get users custom connector in Microsoft Power Automate.
Client Id = Automation Cloud External application’s app ID
Client secret = Automation Cloud External application’s app secret
Authorization URL = UiPath
Token URL = https://cloud.uipath.com/identity_/connect/token
Refresh URL = https://cloud.uipath.com/identity_/connect/token
Scope = Are the scopes you require
The information is available here: Automation Cloud - External Applications (OAuth)