The tag is present in Lintian version 2.104.262. That is the most recent version we know about.
With debhelper compatibility level >= 13 (and also
dh-exec before it) several files in the
./debian folder support the expansion of variables.
Unfortunately, people sometimes confuse the
variables with the similarly-named
Some conditions are difficult to detect but it is never correct
debian/*.install or in
Refer to https://wiki.debian.org/Multiarch/Implementation#Recipes_for_converting_packages and Bug#983219 for details.