On Apple's M-based laptops, the webcam is living in a notch on top of the screen, which Asahi Linux works around by making the usable screen size smaller, so that the notch is hidden in a black bar. But since I paid for the whole screen, I'm going to use the whole screen!
The main obstacle here is that GNOME puts the clock on
the center of the top bar, where it'll be hidden by the notch. Fortunately, a
dnf install gnome-shell-extension-frippery-move-clock will install an
extension to allow moving it to the right of the bar:
Telling the kernel to skip the hack is a simple matter of adding
apple_dcp.show_notch=1 to its command line, by adding it to the
GRUB_CMDLINE_LINUX_DEFAULT variable in /etc/default/grub, running
grub2-mkconfig -o /boot/grub2/grub.cfg to update it, and reboot.