Upgraded from 15.1, t480s display no longer wakes up when selected by KVM, what to attack first?

I have a laptop (lenovo t480s docked to a lenovo dock) and a couple of small desktops, each connected to a common KVM switch.

After upgrading from 15.1 to 15.2, my docked laptop no longer wakes up when selected by the KVM switch. Everything works OK if the laptop is connected to the KVM switch at boot up – Lenovo and Open SUSE splash screens display and then the login screen. But once I switch away to another host and then switch back to the laptop, the laptop never sees activity and the login screen is not displayed (regardless of keyboard tapping and mouse wiggling). After a while, the monitor goes to sleep. If I undock the laptop and lift the lid, there’s the login screen.

My temporary fix is to revert to 15.1.

(Note that the laptop is not sleeping/suspended, it only requires selecting another host for second from the KVM and then switching back. Swapping my KVM for different one does not affect the behavior. Ditto swapping cables and ports.)

I’d appreciate any ideas about how to diagnose this or even what to suspect.