Stuck adding ABUS Prefira Smart Matter Smoke Detector to IKEA Dirigera on UniFi setup

Hey everyone,

I'm pretty new to Matter and smart home setups in general, so I feel like I might be missing something basic here.

I'm trying to pair an ABUS Prefira Smart Matter smoke detector to my IKEA Dirigera hub. The IKEA Home Smart app finds the detector right away during discovery, but then gets completely stuck near the end (after I set a name for the device, the yellow house loading screen never loads, image attached).

Network: Full UniFi setup.

VLANs: Both my iPhone and the Dirigera hub are on a dedicated IoT VLAN.

Connections: Dirigera is wired straight to a UniFi switch. iPhone is on the IoT Wi-Fi SSID.

Firewall/mDNS: Inter-VLAN traffic blocks new connections from IoT to Main (allows established/related). mDNS and IPv6 are both enabled.

I've tried keeping the phone, detector, and hub right next to each other during setup, but no luck.

I’ve also tried restarting/resetting all of the devices with no luck as well.

Has anyone successfully added non-IKEA Matter devices to Dirigera on UniFi? Is there a known quirk with UniFi mDNS or IPv6 multicast during the Thread/Matter handoff, even when both devices are on the exact same VLAN?

Any troubleshooting tips or sanity checks would be awesome!