It’s not just Fibaro. Here’s one regarding the stock zwave multichannel DTH:
So, we were recently forced onto the new SmartThings app since SmartThings Classic stopped working entirely. I have a generic multichannel zwave device (well several of them) that has been setup and working for years in the SmartThings Class app. What I have is a Z-Wave relay with 2 channels, connected to a pair of light switches. In the classic app, it would show the main device and the two child devices allowing me to control individually or together. This was using the Generic Z-Wave Multichannel DTH. In the new SmartThings app, I only see the parent device. When I try to switch it on, nothing happens. In the IDE, it still shows the child devices and the association. I looked through the community threads, but all seemed to be about specific branded devices where the brand provided …