I have compiled a flashable zip that installs the latest modem files. You can download it here.
SHA256: 4f2a6b4acebff7af401fb56fce0ed450155e5958da51f563f0c3ba2418974db8
The zip is based on the official ota zip for Fairphone Open OS 17.04.0, I have simply removed emmc_appsboot, system.img and boot.img, updated the modem files from 17.04.08 manual zip and added some comments to the updater-script.
It is theoretically possible to include this in the Lineage OS zip, but this would require us to manipulate the Lineage OS build process. Providing a seperate zip to update the modem firmware is easier IMHO.