Oof, has there been any official announcement regarding this beyond the release note? If I wasn't so pernickety as to check the notes before every update I'd have been completely unaware and shot myself in the foot.
Is there any possibility of having this added back as an unsupported feature, something that needs to be toggled in the Zigbee settings, perhaps? [EDIT: See testing below.] The Iris V1 devices I have on my C8 are working perfectly, as are many other non-Zigbee 3.0 devices.
Just linking this thread back to the release notes too, in case anybody else is reviewing them and doesn't catch this.
Aye, but this was a whole class of previously supported devices, not just one random doodad.
Can confirm, at least with an AlertMe Smart Plug. On a C7 running 2.3.5.135 it pairs and completes in a few seconds. On a C8 with the same firmware the device is found and initialisation begins, but never completes. 
