Pi 5 does not support 32-bit bootloaders.
Based vaguely on this post, but modified and simplified:
- Do the regular aarch64 installation steps for Raspberry Pi 4, don’t eject yet: https://archlinuxarm.org/platforms/armv8/broadcom/raspberry-pi-4
- Install linux-rpi-16k by force.
- Download it from the link on the sidebar.
- If it gives a 404, try going here and searching linux-rpi-16k and downloading that instead.
- Extract that over your still mounted SD card. Overwrite.
- Sync and unmount.
- Download it from the link on the sidebar.
- Boot your device, SSH into it as usual, set up network, set up pacman, etc.
- Remove old, wrong kernel:
pacman -R linux-aarch64 uboot-raspberrypi - Forcibly reinstall the kernel so that pacman is aware of it:
pacman -Syu --overwrite "/boot/*" linux-rpi-16k - Reboot and pray.