It’s a matter of understanding.
The UX doesn’t have an alternator or a starter. It has two types of battery - a big traction battery that drives the wheels and a small capacity version of the 12V battery on a conventional car. This small one is the one causing your starting problems. It’s only job is to power the door locks, heater and the dashboard so it doesn’t need to be big. That little battery gets charged by the big battery - think of it like one of those powerbanks you can carry to charge your phone and in just the same way, it needs to be connected to the big battery to work. It is only connected when the car is in the READY mode. If you sit in the car waiting or you keep moving it in and out of the garage, you don’t give it time to charge. If you’re having battery problems you might take it for a drive but the only thing that helps is the time, not the distance. You can achieve exactly the same by leaving it stood on the drive but it must be in the READY mode i.e. put your foot on the brake and press start. It may start the engine and it may not - the computer will sort that out but you can reduce the likelihood by switching the heater off. You can also lock the door with the second key. If you are not using the car much, half an hour to an hour once a week will stop you having problems as long as you don’t inadvertently discharge the battery by other means.