Depends on the tech, but essentially you need to adjust stride length, foot pronation/supination, knee extension and a bunch of things about hip alignment.

Someone walking while looking at their phone will ID differently than the same person walking fast while trying not to run.

BUT, in the same context with the same footwear, these systems are pretty accurate. So in places with CCTV, they can be pretty quick at tagging and filtering regular repeated activity. That way, it’s the unrecognized gaits that get flagged up for investigation.

Relevant: https://youtu.be/R46cX0AjzT4

If you walk without rhythm then you won't attract the worn.

If the cameras they use for this are cheap enough to not have an IR filter on them you could maybe blind them with some bright IR LEDs while remaining relatively inconspicuous as long as no one points their phone camera at you.

Like facial recognition it can work under pristine test conditions so you can get governments and corporates to spend millions on it

Not very useful in reality I would assume

Knew this was coming at scale sooner or later. Something of a concern to me personally, because my own gait is particularly identifiable to those who know me.

Aside from footwear, and possibly using various inserts to change the way one's foot falls on the ground, I don't have any obvious thoughts for defeating this unfortunately. The problem with any sort of inserts is that they're likely to cause other problems over time for the same reason they could theoretically mask one's gait - unnatural walking tends to be bad for the body on the whole, and to cause more widespread problems over time.

If I wear boots, sneakers, sandals, hiking shoes sometimes I wonder if it will be enough to throw it off? How distinctly will it be able to tell from millions of gait patterns? Sure it may work foolproof for a set of 100 even intentionally trying to vary things, but how similar will the gait of Roberto Ramirez be to himself the next week or to the hundreds of thousands of people going past an area over a year?

You can very easily fool the machine into recognizing John Cleese.

Put a pebble in your shoe.