What would be required for this to work with systemd-boot?

[sarvasana]

You mentioned your hook will not work with systemd.

Do you happen to know if it is at all possible to have BT working with systemd-boot? I am having great difficulties finding resources on how to get my BT keyboard working at boot time. Need to unlock my luks encrypted disk. For which I can use my laptop keyboard of course, but would really like to use my external keyboard instead.