2023 Kona Electric won't go into Utility mode

Utility mode can only be activated when the car is in "run" mode (and parked), which of course cannot achieved when charging.

 

When charging, run mode can be activated just like when you start the car normally...foot on brake...push start button. This allows HVAC use etc with the energy supplied being diverted from charging the HV pack taking longer to charge. The 12V systems are additionally topped up accordingly.
Utility mode is used when not charging, supplying the HVAC and 12V systems directly from the HV pack, the 12V system is charged at a higher rate (ie 14.6V where normally 13.2V in run mode), similar to what happens when the Hyundai emblem glows yellow periodically after shutdown.
Accessory mode, which can turn on all 12V accessories simply by pushing the start button without foot on brake, is something to be avoided (it may on occasion happen by mistake) is visually indicated on the cluster and sometimes a 12V screen warning. Car is "on" but not in run mode, (no green car with arrows underneath symbol on dash display)
Hyundai was very kind to include the Utility mode and provides a great 12V top up which I use a couple times a month ~2 hours and definitely every time the car is going in for any kind of service.