None. I prefer native packages. AUR usually has me covered and hasn't broken my system...ever, really. Yet, anyways. (Well, it might have broken my Manjaro install, but it is Manjaro, so i probably sneezed wrong)

....but, if I had to pick one? Flatpaks. Outta the three, they've given me the least trouble and just work right out the gate. Still prefer native packages tho