I don’t have personal experience, just reading on these forums quite often when people swap engines and ECU’s - they often find the car won’t start. Usually the advice is the imobiliser - which there are apparently methods to jump ecu pins to bypass. However that doesn’t seem to always be possible.
Another alternative is to desolder and swap over a certain chip on the ecu board…
It seems the primary way to prevent all the issues is to convert take the Immobiliser ecu, key barrel (lock), key, external locks to make the ecu work. I would search the forum first, such as: