If your flooring is attached, like hardwood or tile, you have the option. If it's a floating floor, many of them are not allowed under cabinets (of course you can do what you want but voids warranty). I've seen one LVP that is allowed under cabinets if it's glued down. So if you have flooring picked out that might make your decision for you.

IMO as an installer and remodeler, it's generally a waste to put kitchen flooring under cabinets. Generally by the time you decide to change your cabinet layout, the flooring will be due for an update too. It's very seldom (if ever?) that I've seen someone want to move kitchen cabinets and keep the original flooring.

On the other hand, in higher-wear rooms like bathroom, laundry, mud room etc, I recommend flooring before cabinets because the odds of replacing those cabinets sooner are much higher, and the amount of extra flooring is smaller.