Cannot connect to 2G network using custom ROMs

My Redmi 4X phone was running LineageOS 16 (Android 9) for quite some time until I realized that it cannot connect to the 2G cellular network (GSM only mode). I’ve tried other ROMs, such as BlissROM and crDroid (both Android 11), but the problem still persists. There was one ROM (ReloadedOS, Android 10) that did manage to connect my phone to 2G, but I decided to get out of that ROM due to other problems I’ve discovered.

In any of the ROMs I’ve tried, when I select LTE only, my phone almost immediately connects to the network. So, what could be the source of this problem — the phone, the ROM, the kernel, or something else? I really need to access 2G networks as LTE cannot penetrate inside my house, so I don’t get texts or calls that may be important.