I had a home 4G router for a while, a TPLink 200 something. The 4G modem inside was a full Android device ! See here https://openwrt.org/toh/tp-link/archer_mr200?datasrt=%5Efirm...

I didn’t check, and on mobile now. But I would be very surprised if that was the actual baseband (more just a wrapper around it).

So I got a little bit of time to check (https://github.com/Biktorgj/quectel_eg25_recovery/tree/EG25G... - the NON-HLOS), and it's still actually running a Qualcomm Hexagon baseband (40mb binary by Qualtec when combined using Gal's unify_trustlet script).

Load that into Hexagoon IDA plugin and you'll see it's bog standard Hexagon for all the remote GSM/LT code that actually does stuff (similar to the project zero research). I haven't verified (and don't own a Pinephone) but most Quectel boards I've seen in the past do enforce signature validation, so binary patches are not easy.