It could be the electronic switch per se but that will not be turned on unless the tumbler can rotate far enough (if the small springs and so on are damaged).
With mine, you could turn it somewhat (1 and 2) but it could not be pushed to 3 (before it would normally be clicked back towards 2 after the starter turned the engine over and successful cylinder ignition occurred).
I tried gentle tapping with a small hammer, a lot of dilithium grease, hard strikes with a big hammer and I gave up.
The barrel and switch are more or less one unit even if they are sold and installed as separate parts. They complete a circuit. I would replace both even if they are separate and one "still works".
The only other issues I can think of are bad contacts (battery [unlikely, you probably checked this over and over again], switch, ignition or sensors), an
ECU issue or the relay switch. If you have a no start, no cranking condition it probably isn't the relay. You can probably test the relay with a multimeter or a circuit tester. I checked my fuse box and they were all fine.
I had to call in the NRMA. I always find it embarrassing but I love chatting to the towies when they give you a lift, they probably think I'm a nuisance like a hypochondriac at a doctor's.
If you're in a bigger place, you might be able to get the barrel replacement in less than a day.