This bug report is tagged "newcomer" as it a good bug where you can learn about
debian/rules and dh.

debian/rules currently uses a rather lengthy hand-written sequencer for
debhelper tools. Current practice is to use a much shorter one as described at

file:///usr/share/doc/maint-guide/html/dreq.en.html#rules
https://www.debian.org/doc/manuals/maint-guide/dreq.en.html#rules

Where needed, use execute_after_dh_<command>, execute_before_dh_<command>, or
even override_dh_<command> to recreate the original flow as closely as possible.

In the second step you could then trim away any commands that are there for
historical reasons and not needed.