Fibocom L831-EAU-00 won't show in Solus, but works fine in Ubuntu

Hi,

I'm using a Lenovo Thinkpad x270 that has the Fibocom L831-EAU-00. I recently received an extra data card from my mobile carrier, but it does not work in Solus Linux. Testing the card and modem in an Ubuntu 19.04 live usb works perfectly.

Neither nmcli d s nor mmcli -L show any gsm-modems available at all.

In lsusb the modem seems to be identified by Bus 001 Device 002: ID 2cb7:0002. It does not have an identifying name or model in Solus nor Ubuntu.

I have been troubleshooting with the Solus devs for some time and they think it might be a ModemManager bug of some sorts.

What I know so far:

According to the Solus devs, this is not a kernel issue as the modem seems to be loading fine when reloading the cdc_mbim module through modprobe:

dmesg output after reloading

[   20.380748] cdc_mbim 1-3:1.0: nonzero urb status received: -EPIPE
[   33.751443] cdc_mbim 1-3:1.0: nonzero urb status received: -EPIPE
[   33.751670] cdc_mbim 1-3:1.0: nonzero urb status received: -EPIPE
[   43.764904] usbcore: deregistering interface driver cdc_mbim
[   43.765016] cdc_mbim 1-3:1.0 wwp0s20f0u3: unregister 'cdc_mbim' usb-0000:00:14.0-3, CDC MBIM
[   43.787664] usbcore: deregistering interface driver cdc_ncm
[   43.808431] usbcore: deregistering interface driver cdc_wdm
[   50.576373] usbcore: registered new interface driver cdc_ncm
[   50.578222] usbcore: registered new interface driver cdc_wdm
[   50.628739] cdc_mbim 1-3:1.0: setting rx_max = 16384
[   50.629772] cdc_mbim 1-3:1.0: cdc-wdm1: USB WDM device
[   50.630338] cdc_mbim 1-3:1.0 wwan0: register 'cdc_mbim' at usb-0000:00:14.0-3, CDC MBIM, d2:98:08:c1:98:65
[   50.630531] usbcore: registered new interface driver cdc_mbim
[   50.638140] cdc_mbim 1-3:1.0 wwp0s20f0u3: renamed from wwan0
[   64.818470] show_signal_msg: 5 callbacks suppressed
[   64.818473] gdbus[2156]: segfault at 20 ip 00007fbf60d56847 sp 00007fbf530dd528 error 4 in libc-2.29.so[7fbf60bfc000+170000]
[   64.818478] Code: 48 83 e7 e0 48 01 ca 48 81 ea 80 00 00 00 0f 86 0a 01 00 00 eb 5e 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 83 e1 1f 48 83 e7 e0 <c5> fd 74 0f c5 fd d7 c1 d3 f8 85 c0 74 1b f3 0f bc c0 48 39 c2 0f

I will be helpful for testing out any tips you might have to fix this error, if possible.