They are upstreaming their patches, so upstream Linux will eventually get the necessary drivers.

Though their kernel fork is (obviously) open source, so there's nothing stopping you from taking a Debian aarch64 roots, build your own Asahi kernel (or take the build from Fedora), and set up Debian on these machines with Debian yourself. Just requires some elbow grease.

Or, if you find Ubuntu acceptable, there's Ubuntu Asahi: https://ubuntuasahi.org/

EDIT: After some googling I found this wiki article: https://wiki.debian.org/InstallingDebianOn/Apple/M1