During the boot, ng_ubt(4) is autoloaded and I see errors:

ubt0 on uhub0
ubt0: <MediaTek Inc. WirelessDevice, class 239/2, rev 2.10/1.00, addr 2> on usbus0
ubt1 on uhub0
ubt1: <MediaTek Inc. WirelessDevice, class 239/2, rev 2.10/1.00, addr 2> on usbus0
ubt1: ubt_attach:671: could not get two interfaces
device_attach: ubt1 attach returned 6
ng_hci_process_command_timeout: ubt0hci - unable to complete HCI command OGF=0x3, OCF=0x3. Timeout

Since this controller requires firmware patch downloading to operate,
block ng_ubt attachment unless operational firmware is loaded.