I built a custom OpenWrt image for my 5G Modem CPE (specifically targeting devices like the FiberHome UX2000 (DITO WA2000), powered by an MT7621A + MT7615 DBDC layout) using Hermes Agent paired with the Hy3 model.
So far, I've only tested it with Quectel 5G cards using an M.2 B-Key interface (such as the RM500U-CNV). Keep in mind that for the cellular/modem side of things, you will need to write or tailor specific connection and initialization scripts depending on the protocol your card require