I spend quite a bit of time on getting a Sierra Wireless EM7345-LTE modem to work under Linux. So here are some quick instructions to help other people who may hit the same problem.

These modems are somewhat notorious for shipping with broken firmware. They work fine after a firmware upgrade, but under Windows they will only upgrade to "carrier approved" firmware versions, which requires to be connected to the mobile-network first so that the tool can identify the carrier. And with some carriers connecting to the network does not work due to the broken firmware (ugh). There are a ton of forum-threads on how to work around this under Windows, but they all require that you are atleast able to register with the mobile-network.

Luckily someone has figured out how to update these under Linux and posted instructions for this. The procedure is actually much more straight forward under Linux. The hardest part is extracting the firmware from the Windows driver download.

One problem is that the necessary Intel FlashTool download is no longer available for download from Intel. I needed this tool a while ago for something else, and back then I used the PhoneFlashTool_5.8.4.0.rpm file from https://androiddatahost.com/nm466 . The rpm-file in the zip there has a sha256sum of: c5b964ed4fae470d1234c9bf24e0beb15a088a73c7e8e6b9369a68697020c17a

I now see that it seems that Intel is again offering this for download itself, you can find it here: https://github.com/projectceladon/tools and projectceladon seems to be an official Intel project. Note this is not the version which I used, I used the PhoneFlashTool_5.8.4.0.rpm version.

Once you have the Intel FlashTool installed just follow the posted instructions and after that your model should start working under Linux.