This diff lists Quectel RM500Q as supported for umb(4).

Switching to MBIM mode is done by issuing AT commands
(AT+QCFG="usbnet",2 and AT+CFUN=1,1) over the serial port.

umb0 at uhub0 port 5 configuration 1 interface 4 "Quectel RM500Q-AE" rev 2.10/4.14 addr 3

umb0: flags=8851<UP,POINTOPOINT,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        index 7 priority 6 llprio 3
        roaming disabled registration home network
        state up cell-class LTE rssi -101dBm speed 1.1Gbps up 3.0Gbps down
        SIM initialized PIN valid (3 attempts left)
        subscriber-id 466xxxxxxxxxxxx ICC-id 8988xxxxxxxxxxxxxxxx
        device RM500Q-AE IMEI 867xxxxxxxxxxxx firmware RM500QAEAAR13A02M4G
        APN internet provider TW Mobile provider-id 46697
        dns 61.31.1.1 61.31.233.1
        groups: egress
        status: active
        inet 10.93.21.217 --> 10.93.21.218 netmask 0xfffffffc

ok?

Index: share/man/man4/umb.4
===================================================================
RCS file: /cvs/src/share/man/man4/umb.4,v
retrieving revision 1.16
diff -u -p -u -p -r1.16 umb.4
--- share/man/man4/umb.4	21 Feb 2023 07:47:24 -0000	1.16
+++ share/man/man4/umb.4	1 Jan 2024 09:00:50 -0000
@@ -56,6 +56,7 @@ The following devices should work:
 .\" .It Huawei ME906s -- attaches but needs more work
 .It Medion Mobile S4222 (MediaTek OEM)
 .It Quectel EC25
+.It Quectel RM500Q
 .It SIMCom SIM7600
 .It SIMCom SIM8262E-M2
 .It Sierra Wireless EM7345