Use licenses from /usr/share/common-licenses/

[kornelski]

https://lintian.debian.org/tags/copyright-should-refer-to-common-license-file-for-gpl.html

[infinity0]

In general it's best to create Debian source packages (.dsc) rather than binary .debs directly. debcargo is the official Debian crate-to-package converter we're using which takes this approach, and points to licenses from /usr/share/common-licenses like you want here.