ZTE MF286R - cellular modem connects to network, but no IP or internet access in OpenWrt

Hello, I'm trying to get the cellular modem on this MF286R to work.

I have installed 3ginfo and luci-app-3ginfo. The Details tab looks like this when trying to use ModemManager, when using just ncm it looks the same, but with some connection statistics (a few kB sent up and down):


Don't mind the useless edit to hide the Cell ID and LAC. Yes, I'm terrible at opsec.

USB debug information:

T:  Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480  MxCh= 1
B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev= 5.15
S:  Manufacturer=Linux 5.15.134 ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=1b000000.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms

T:  Bus=01 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  2 Spd=480  MxCh= 0
D:  Ver= 2.00 Cls=ef(misc ) Sub=02 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=19d2 ProdID=1489 Rev=ff.ff
S:  Manufacturer=ZTE
S:  Product=ZTE
S:  SerialNumber=123456789ABCD
C:* #Ifs= 6 Cfg#= 1 Atr=e0 MxPwr=  2mA
A:  FirstIf#= 0 IfCount= 2 Cls=e0(wlcon) Sub=01 Prot=03
A:  FirstIf#= 2 IfCount= 2 Cls=02(comm.) Sub=02 Prot=01
I:* If#= 0 Alt= 0 #EPs= 1 Cls=e0(wlcon) Sub=01 Prot=03 Driver=rndis_host
E:  Ad=82(I) Atr=03(Int.) MxPS=   8 Ivl=1ms
I:* If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=rndis_host
E:  Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=01(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 2 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=01 Driver=cdc_acm
E:  Ad=84(I) Atr=03(Int.) MxPS=  10 Ivl=32ms
I:* If#= 3 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=cdc_acm
E:  Ad=83(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 4 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=ff Driver=(none)
E:  Ad=85(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=03(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
I:* If#= 5 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=42 Prot=01 Driver=(none)
E:  Ad=86(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=04(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms

T:  Bus=02 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=480  MxCh= 1
B:  Alloc=  0/800 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 2.00 Cls=09(hub  ) Sub=00 Prot=01 MxPS=64 #Cfgs=  1
P:  Vendor=1d6b ProdID=0002 Rev= 5.15
S:  Manufacturer=Linux 5.15.134 ehci_hcd
S:  Product=EHCI Host Controller
S:  SerialNumber=1b400000.usb
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=256ms

Configuration (is it supposed to show "Absent interface: wan"? ):

I have checked that the APN is correct and the SIM card does not have a PIN. The modem device is /dev/ttyACM0 and I have checked that it responds to AT commands:

AT
OK
ati
Marvell

When using ModemManager, the "wwan" cellular interface I have created just shows "Error: Connection attempt failed." in luci.

mmcli -m 0:

  --------------------------------
  General  |                 path: /org/freedesktop/ModemManager1/Modem/0
           |            device id: 10b4df4d15798b8e64c56cc78c4c027b6fd6a471
  --------------------------------
  Hardware |         manufacturer: Marvell
           |                model: LINUX
           |    firmware revision: BD_MF286MODV1.0.0B03
           |            supported: gsm-umts, lte
           |              current: gsm-umts, lte
           |         equipment id: [ID]
  --------------------------------
  System   |               device: /sys/devices/platform/ahb/1b000000.usb/usb1/1-1
           |              drivers: cdc_acm, rndis_host
           |               plugin: zte
           |         primary port: ttyACM0
           |                ports: ttyACM0 (at)
  --------------------------------
  Status   |                state: disabled
           |          power state: on
  --------------------------------
  Modes    |            supported: allowed: 2g; preferred: none
           |                       allowed: 3g; preferred: none
           |                       allowed: 4g; preferred: none
           |                       allowed: 2g, 3g, 4g; preferred: none
           |              current: allowed: any; preferred: none
  --------------------------------
  IP       |            supported: ipv4, ipv6, ipv4v6
  --------------------------------
  3GPP     |                 imei: [IMEI]
           | packet service state: detached
  --------------------------------
  3GPP EPS | ue mode of operation: csps-2
  --------------------------------
  SIM      |     primary sim path: /org/freedesktop/ModemManager1/SIM/0
  --------------------------------
  Bearer   |                paths: /org/freedesktop/ModemManager1/Bearer/0

When using NCM, a few kB are sent through the wwan interface, wwan_6 and wwan_4 interfaces are created. None of those interfaces get any addressing, though, so there's no internet connectivity. I have tested both the IPv6 only "internetipv6" APN and the old IPv4 only "internet" APN for my ISP, both result in no addressing of any kind.

I would really appreciate any help on how to get this modem working.