LTE PCIe modules

Are there any LTE PCIe modules (The small key ones that fit in a FW4B protectli unit) that work as a red failover in ipfire?

Did you consult the HCL?

There are a few on it, but generally anything that emulates a serial modem works.

I tried and failed however having a more determined look I’ve spotted the Huawei ME909u-521 in that list

That’s a good one