Check out diyHue to use the Hue app with Zigbee2MQTT without a physical Hue bridge. I've been running it for almost a year with zero problems using the Hue Essentials app. Source: over 1 year ago

Finally, I'd like to mention DiyHUE, (HA addon and integration availables) which is basically a HUE emulator that allow you to add a lot of non-hue lights into the HUE ecosystem, and control them using the official HUE app, which has a really nice UI and the whole "hue labs" formulas and custom effects included, which is awesome. Source: over 1 year ago

Maybe diyHue is what you're looking for. As a warning, consider it in alpha stage. Source: about 2 years ago

There’s a few projects out there like this: https://openrgb.org/ and https://diyhue.org/ there’s probably a few others too. Source: over 2 years ago

Ther also exists a Hue Bridge emulator called DIYhue. I didn‘t try it yet but it seems promising. This Software can run on a Pi and emulates a Hue Bridge. Therefore your official Hue app can discover it. On the other end the Software connect with the real Bridge but also with third party devices. For example over the ConBee II ZigBee USB Stick. Source: over 2 years ago

But now it is finally available - Hue Log. App Store. Webpage. Source: 8 months ago