Instructions for binding in the Home Assistant Matter Server:
First, find the Node IDs of the two switches you are binding. Go to Settings > Devices > Matter > select each device (node ID is located under Device Info).
Go to Settings > Add-ons > Matter Server > Open Web UI.
Select the control Node > Endpoint 2 Dimmer Switch > Binding > Binding (in the column at the top).
Enter the target’s Node ID, Endpoint 1, Clusters 6 and 8. Cluster 6 is for state changes between on and off, and cluster 8 is for brightness. If you don’t want brightness to be bound, then don’t include cluster 8.
Note: at this time matter binding only works for physical presses of the switch. If the control light’s state change comes from Home Assistant (eg, via voice control, the HA dashboard, or an automation), this bypasses the matter binding and nothing will happen to the target light.