Sierra Wireless EM7411 LTE modem support?

I’m trying to get a built-in LTE modem working. It’s a Sierra Wireless EM7411. It’s in a box 8552km away from me so physical and power-cycle is not exactly easy.

1: ModemManager doesn’t handle the modem. As far as I can tell it’s because it assumes the modem is in MBIM mode which has not been the default for a long time. I’m also hesitant changing the mode in case of bricking it.
2: Guides on the internet about EM7411 are quite old and don’t take into account that the communication has changed from ppp (I think) to raw-ip, nor that --device-open-proxy appears to be mandatory now.

What I do is I get the connection going with the QMI control interface (“qmicli”) with ip link set up, --wds-start-network, --wds-get-current-settings, starting udhcp directly (only DHCP client with raw-ip support), etc. Sometiems it works. Sometimes it works for eg. 40 minutes, sometimes it seems to work forever. The problem is that when it doesn’t work or stops working it appears that a power-cycle is needed (neither --wds-reset nor reboot seems to do it).

Has anyone gotten an EM7411 modem to work on a recent distribution? An up-to-date howto, or a messy but reliable script, or any additional information would be greatly appreciated.

The end goal is to use the LTE connection as backup connection in case ethernet doesn’t work, or as primary-and-only connection in remote areas, so power-cycle is not really an option.

The current non-functioning state is that packets are sent on the wwan0 interface:
ltetest:~ # ip -s link show dev wwan0
2: wwan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 1000
link/ether 8a:a0:a3:b5:e8:e4 brd ff:ff:ff:ff:ff:ff
RX: bytes packets errors dropped missed mcast
0 0 0 0 0 0
TX: bytes packets errors dropped carrier collsns
18642 193 0 0 0 0
altname wwp0s20f0u10i8

but the device statistics say otherwise:
ltetest:~ # qmicli --device=/dev/cdc-wdm0 --device-open-proxy --wds-get-packet-statistics
[/dev/cdc-wdm0] Connection statistics:
TX packets OK: 0
RX packets OK: 0
TX packets dropped: 0
RX packets dropped: 0
TX bytes OK: 0
RX bytes OK: 0
I also spoke to the carrier, and as far as they can see no packets have been sent on the PDP context.