Both loading a dishwasher and learning to wash up by hand. When they move out there might not be a dishwasher.
I moved in to a shared flat the day after the dishwasher repair man had been, and he told the two who had already moved in not to use washing up liquid in the dishwasher.
How to 'solve' things eg if the dishwasher has stopped working that you can use the powder to hand wash, you don't get suds but it works.
\I have always been able to follow a recipe and I knew a few things from home but I actually learned to cook properly by watching, 'ready, steady, cook'.
So not just shopping for ingredients, cooking and cleaning up afterwards but open the fridge / cupboards and make something out of the contents.
Know how to do things without tech, that you can use a watch as a compass, read a paper map / timetable / use a pay phone (all though they are dying out).
How to eat politely with cutlery, chopsticks and hands. You never know where you will end up in life.