Erkkk I did a really silly thing and, since the new camera-ui kept crashing, I . . . attempted to uninstall it. But pretty soon after removing the camera-ui package, reboot loop! Even after reflashing the kernel it's still stuck in a reboot loop; I'm going to have to reflash the eMMC as well, aren't I? Or perchance is there any other way?

Edit: Of course, in my panic I forgot entirely that inbetween flashing just the kernel and flashing the entire filesystem there's also just flashing rootfs, durr. So tried that, and---okay, after another reboot it seems alright. Phew. Note to self: avoid being such an idiot in future