Bridge Configuration using qmi modem in 5G campus net

Hi there,
I successfully setup my Quectel RM500Q 5G modem using QMI Cellular. As I'm connected to a 5G campus net I wanted to setup my OpenWRT device in a bridge configuration. I've tried using the relayd package, however the bridge doesn't seem to work. For the Relay Bridge I've selected a local IPv4 address within 5G routers subnet and made sure it isn't in it's DHCP range. I'm using a Raspberry Pi 4 as my OpenWRT device in case it matters.
Has anyone configured a QMI modem in a bridge configuration and could help me out?

Any help is appreciated!

Kind regards,
Julian