Ah, looks like the registrars were still coming online when I tried. When I first tried Gandi, it didn't seem to like .app, but now it does and lets me choose "

Ah, looks like the registrars were still coming online when I tried. When I first tried Gandi, it didn't seem to like .app, but now it does and lets me choose "landrush," which I assume is the way to buy a domain during the EAP.