EASA doesn't have rules for ultra- and microlight aircraft, they're only in national regulations. So then it depends on what the country you're in decides.
But even if you're allowed to fly with only minutes of fuel reserve. The big question is whether you should want to. When you're in a more basic aircraft, that didn't go through all the certification requirements that other aircraft go through, it would not be a great idea to skip all kinds of safety practices like fuel and alternate planning just because you're not legally forced to do it. You're then just increasing risks more and more, while this thing is marketed to non-pilot buyers that may not even fully understand the risks.