The one thing I noticed that might be of interest here is that Matter 1.4 includes " in-wall mounted switching for lights and fans." I don’t have any of the Inovelli Matter switches, so I’m not sure how that would or would not change the way the switches behave.
I just did the upgrade. My only White Series switch still works.
This version is still labeled beta. The only change that I noticed was the addition of a “Matter Server” entry on the left menu bar of the main HA screen, that allows you to drill down into each device’s endpoints. Maybe this function was there all along and I just missed it???
No change in behavior or capabilities. In the case of a dimmer, previously devices were tagged as being either a dimmable light (type 0x0101 - which is really meant for bulbs), or a plug-in unit dimmable unit (type 0x010B). An in-wall dimmer switch is technically neither a light bulb, nor is it a plug-in unit, so there was some ambiguity about what type a vendor should choose. These new types in Matter 1.4 resolve that ambiguity by providing a device type that is more clearly matched to wall switches - i.e., the mounted switch type (type 0x0110). All 3 types (0x0101, 0x010B, and 0x0110) have the exact same collection of control clusters and attributes so they all have the same capabilities. Think of this change as simply letting the controller user interface know which device icon is most suitable when you see the control on a UI. I.e., this is a minor change.
And the type of the device is fixed in the firmware, so there is no change anyway for the Inovelli 2-in-1 (at last not until a Matter 1.4 firmware update).