"Bluetooth Device Did Disconnect" does not work

Still doesn't work.

I just tried with my MX Master 3S, and indeed I don't receive any disconnect notifications for that one either although BTT seems to correctly register for them. Connect notifications seem to work fine.

Very interesting, the system report also keeps thinking the device is connected.
Maybe modern logitech devices don't really disconnect, but go into some sort of sleep mode?

Does yours also keep showing up under "connected" in System Report, although it has disconnected / is turned off?

On my Mac it displays that they are disabled. Even when I completely disable Bluetooth it does not perform the action. Maybe it would just be possible to somehow integrate BTT with Logi+?

No, Logi+ doesn't offer any such integration. However I'm working on full Logitech support to be able to replace the Logi+ app completely, but that will still take until the end of this year.

I think for these kind of bluetooth devices I could switch to HID notifications instead of bluetooth notifications though. They seem to be more reliable.

Yeah, the system report shows enabled, while in Settings it is shown correctly as disabled.
Meaning, the system report is not updated when opened, but the settings menu does update correctly.
When I close and re-open the system report, then the status is shown correctly.