The latest C7 firmware update has given me the opportunity to revisit my zigbee lighting setup, so I wanted to share the results of a lengthy process of updating and rechecking IKEA Tradfri bulb compatibility...
On the latest firmware 2.3.3.127, and on the latest 'Zigbee 3.0' firmware from IKEA - updated via thier hub, I'm now able to use all current models in the IKEA Tradfri bulb lineup with the Hubitat built-in Advanced Zigbee Drivers - including PowerRestoreState setting (although with some there is a momentary low level on/off). This applies to the CWS(RGBW) bulbs too.
I'll write up a table of what I've tested, model numbers, and IKEA firmware version in use if anyone is interested.