I downloaded the 64-bit Raspberry Pi OS Lite image from https://www.raspberrypi.com/software/operating-systems/#raspberry-pi-os-64-b... and mounted the 2023-12-11-raspios-bookworm-arm64-lite.img. In /rootfs/etc/apt/sources.list and /rootfs/etc/apt/sources.list.d/raspi.list, I see 3 debian repos and 1 raspberrypi repo: deb http://deb.debian.org/debian bookworm main contrib non-free non-free-firmware deb http://deb.debian.org/debian-security/ bookworm-security main contrib non-free non-free-firmware deb http://deb.debian.org/debian bookworm-updates main contrib non-free non-free-firmware deb http://archive.raspberrypi.com/debian/ bookworm main There's some good info at https://forums.raspberrypi.com/viewtopic.php?t=333285, like "Raspbian is only armhf. There is no 64-bit Raspbian. It is the main reason why the official images were renamed Raspberry Pi OS when the 64-bit images were introduced.".