I'm able to get 5G on the stock Android 13 and Android 15 from Fairphone without an issue, but if I install the stock Android 11 from Fairphone, I lose 5G and I'm stuck on Edge service (at best).

Installing Android 15 to check if this is a version issue, I'm guessing with the modem firmware, I find that 5G works just fine, and installing the Android 13 stock firmware works fine, as does LineageOS.

Is there any way to identify the exact cause, and resolve it, potentially by using the firmware .bin file from a newer Android OS version, (or however exactly it works)?