[Shank]

You can use Command + Option + R to boot internet recovery instead of the on-disk recovery. That'll download and install the latest version of the operating system associated with your Mac.

On the 2fa front: if you only have one Apple device, you really can't leverage the Apple 2fa system, I think. It always requires a past Apple device of some kind to get the code.

[test1235]

ah .. I didn't know about internet recovery. Hopefully, I'll remember your tip if this happens to me again (I borrowed an iPad, in the end).

Unfortunately, it doesn't look like you can turn off 2FA once you've had it on for some time, so it feels like I'm being pushed into buying a second Apple device?