Yeah, OpenSSH does looks at ~ for the .ssh directory, but I don't remember if it honors HOME, or check the passwd file.
IIRC, my build looks for the global one in /mnt/us/usbnet/etc, so I'll try with that.
This is a pretty specific piece of software for a pretty specific usage, I don't think it needs more hand-holding than this

. If it works as it should when used properly, done!

.