Does that not show up under Settings → Add-Ons? Or give you a config option to “show in sidebar”? Honest question; I’ve got a Yellow and still coming to grips with the many moving parts of HA.
Well the WebUI of the Matter Server is my first answer 
I knew of the Inovelli one because of the community forums for that product.
There’s always trial-and-error 
Many devices only have one endpoint (okay, 2, if you count endpoint 0 which is purely for management). So unlikely the endpoints reach a particularly high number. Brute force each one and see which gives you the desired result. 