https://bugzilla.redhat.com/show_bug.cgi?id=2071646
--- Comment #8 from Zbigniew Jędrzejewski-Szmek zbyszek@in.waw.pl --- Maybe the following:
BuildRequires: jdupes
%prep: ... sed -i /gzip/d do_install
%install: ... jdupes -r -l %{buildroot}%{_mandir}
This has also the advantage that the distro compression settings are used. gzip is now used by default, but I think we'll be switching to zstd at some point.