Wheel swap - tyre pressure monitor system

Hi all, picked up my new-to-me A7 yesterday and am very pleased with it.
It’s got the 21” rotor wheels which I think are too big, not doing much for the ride (yes I’m an old git) plus new tyres are frighteningly expensive.
I’m therefore contemplating fitting 20” blade S7 wheels if I can find any because they’re my favourite OEM design - question is what happens if you fit a set without TPMS inside?
Constant alarms that’d drive you up the wall, or does the system just stay silent and report ‘no sensors’ in the relevant dash menu?

A-ha! MMI does offer a 'click here when you checked your pressures are ok' message - I suppose I should really read the manual instead of asking daft questions - now I've looked it does indeed work off the ABS.
What threw me was ebay adverts stating TPMS included on used wheel sets. Ta!
Oh, and you have excellent taste - Mythos Black here too