No Cellular Signal; hardware issue?

iPhone X (ATT) model had a cracked back glass that was pretty extensive and missing some pieces of the glass. This was the only damage to the phone; however, the phone worked just fine for the last six months.

Recently, the phone is unable to get any cellular signal. This appears to have happened overnight. WiFi and Bluetooth still work. The SIM card still reads. When I remove the SIM card and place it into another phone the cellular signal works. So this isn’t an ATT problem or a service outage in the area problem.

I’ve since replaced the back of the phone from another iPhone X and switched over all of the hardware, ensuring clean points of contact to the frame but without any improvement. This was to rule out the physical frame antenna as a culprit.

I’ve also replaced the cellular antenna at the bottom of the phone to rule out a faulty cellular antenna and also without any improvement.

I’ve performed a full reset of the phone twice now, as well as a network reset and no improvement.

I’m down to only two more options; either the interconnect ribbon is bad, or the logic board is somehow damaged. Replacing the interconnect ribbon is the next cost-effective choice or sending the phone out for repair on the logic board since this outside of my capabilities.

Was curious if anyone else has had a similar problem, or should I be looking for a new used iPhone X?