I have a USB drive with the key on it. The primary purpose for LUKS for me is so that drives I replace don’t need to be wiped, so I just leave the USB drive in all the time. Makes it so it boots automatically.

If I lived in a place I owned, I’d stash a rpi somewhere deep and have it do network dropbear automatic unlock to protect the data if the server is nicked. Till then it’s yolo