Just thought I’d share my success in getting an IKEA Trådfri bulb paired to a Philips Hue hub WITHOUT using the IKEA gateway, I don’t even own an IKEA gateway. I bought the bulb today (batch 1729) and using the pair method of switching the lights on and off 6 times the bulb successfully appeared in the Hue app and is fully controllable via the Hue app, Alexa, Home (iOS app via Homebridge) and of course Home Assistant.
I believe any bulb of batch 1721 and up will work. See photos.