Use dpkg-maintscript-helper with literal "$@" according to the comments in https://bugs.launchpad.net/ubuntu/+source/linux-firmware/+bug/630748/comments/68
Use dpkg-maintscrip t-helper with literal "$@" according to the comments in https:/ /bugs.launchpad .net/ubuntu/ +source/ linux-firmware/ +bug/630748/ comments/ 68