Comment # 21 on bug 1170443 from Stanislav Brabec

There is a strange change:

Leap 15.1:
rpm -qlvp util-linux-2.33.1-lp152.4.55.x86_64.rpm 2>/dev/null | grep
/usr/bin/su
-rwsr-xr-x    1 root     root                    59520 dub 14 16:44 /usr/bin/su
   ^

Tumbleweed:
rpm -qlvp util-linux-2.35.1-1.1.x86_64.rpm 2>/dev/null | grep /usr/bin/su
-rwxr-xr-x    1 root     root                    51320 dub 15 20:10 /usr/bin/su
   ^

There was not any relevant change in the spec file. Maybe in rpm or so.

It did not have SUID flag in
/home/abuild/rpmbuild/BUILDROOT/util-linux-2.33.1-0.x86_64/usr/bin/su

But anyways, the change should not affect, as permissions are set by:

%post
...
%set_permissions %{_bindir}/su                                                  

You could check your installation log. Maybe this command failed or you set
paranoid security profile.

/etc/permissions.paranoid:
/usr/bin/su                                             root:root         0755