Ding ding ding ding. And if there is pre-detonation happening, you can feel it. And the sensor will tell you as well. So it's all good and there is kumbayah in the valve train.
I thought modern ECUs (and yes, the LR3 should qualify as having a "modern" ECU), the system will adjust timing and mixture on lower octane fuel to impede knock, so you would not notice pinging/knocking unless you have a problem with the ECU or fuel injectors. What you
may notice is reduced power from non-optimal mixture and timing.
I drove a straight-six turbo Volvo for years that recommended 91+ octane (in Colorado, generally 91 is the highest you can get - altitude is the factor there). When we very rarely required a tank of less-than-91 octane due to availability or whatever, by the second start it was a little slower off the line and less responsive on tip-in, and the engine sound was only very slightly off (not rough, just different, wheezier maybe), but it never pinged or knocked.
Here's an article from 2001 where empirical tests were done on different cars:
https://www.caranddriver.com/features/a15138486/regular-or-premium/
Here's the opinion of a GM fuel system engineer:
https://jalopnik.com/why-putting-regular-gas-into-a-car-that-needs-premium-w-1796463139
