In general browsers attempt to establish a HTTPs-Connection if possible. How would you force a browser to fallback to HTTP when somebody enters asdf.xyz in the search bar of his/her browser without specifying a protocol?
Therefore: sslstrip is probably not helpful as there are no links to "fake". Furthermore, it is assumed that the site does not use HSTS.
Assuming one can perform MITM - how would the routing with iptables be performed/which commands would you need to make the browser believe that HTTPs is not available and to fallback to HTTP?