@Mike I have no hard evidence about the magnetron being faulty, however this was the diagnosis made by the tech guy who came over to fix it.
The whirlpool oven displays error F05 (which I was not able to find anywhere in my research over the internet). It displays it only when using features that relay on microwawes, other than that it works fine.
The "official repair guide" - which I have not seen - seems to state that to fix error F05 it is needed to replace the inverter board and the magnetron.
Since the tech guy had a spare new inverter board, he switched it and left it in the oven, unfortunately that didn't fix the error. That's the reason why I am assuming it's the faulty magnetron.. I am actually hoping that, trusting that the tech guy placed a working inverter board inside my oven.

Thank you for your inputs, you're being really helpful