Not well known, but if you navigate to /[your peplink ip]/MANGA/support.cgi on a PepWave device, there are options to upgrade your cellular modem firmware.
I recently tried this, and almost bricked the device!
At first, it seems OK: it downloads the firmware update, and starts updating.
But then it gets bad: while upgrading the modem firmware, the modem drops offline, naturally.
But the upgrade process has 5 steps.
So after step 1, it fails to download step 2. It also says “don’t power down” or else.
I was quite lucky in that I had done the 30 day trial which enables WAN on ethernet. So I ran around and found a 100’ ethernet cable which I dragged out to my RV to complete the modem firmware upgrade.
Suggestion: if a pepwave device has only cellular modem connectivity, it should not offer to do a modem upgrade that might brick it.