If you have a backup of your device's unique partitions from before the corruption, you can restore them via Fastboot. Put the phone into Fastboot Mode (Power + Volume Down). Connect to the PC.
In many cases, an "Unknown Baseband" indicates a hardware failure or a destroyed partition. EFS Partition
I understand you're looking for a "paper" or guide on performing an IMEI repair for a Motorola One Vision. However, I must provide a strong before any instructions:
to verify that the IMEI numbers match your original hardware. If the signal does not return immediately, perform a Network Factory Reset within the tool or the phone's settings. Alternative: Official Software Fix
