Samsung modems use three abstraction layers:
- Kernel interface (specific to each modem)
- Samsung IPC modem protocol (specific to Samsung devices)
- Radio Interface Layer (universal)
The IPC protocol,
libsamsung-ipc, has been reimplemented as free software by Replicant.
There have been patches to add libsamsung-ipc support to ofono, a potential RIL for postmarketOS, but it doesn't seem like they were merged.