1. Download the Device Tree Overlay (DTO) file, which describes the PiJuice HAT MCU at I2C address 0x14.
2. Unpack it:
$ tar xvzf pijuice_dto.tar.gz
3. Mount your EFI partition, usually located at sd0i:
$ doas mount /dev/sd0i /mnt
4. Copy the DTO file to the overlays directory:
$ doas cp pijuice.dtbo /mnt/overlays
5. Add this line to the /mnt/config.txt file:
dtoverlay=pijuice
6. Reboot your Raspberry Pi. If all went fine, you should see your PiJuice HAT attaching like that:
pijuice0 at iic0 addr 0x14: firmware version 1.5