Currently I have issues with mixed content on one of the site I am testing and trying to resolve it. To resolve mixed content I was able to add the following to HAProxy in PFSense:
Modifying Header in PFSense (Firewall) in HAProxy Backend (Best Method so far I found)
Header always set Content-Security-Policy: upgrade-insecure-requests
by doing so I am able to resolve most http to https and solve mixed content issues for images, links, etc. but it seem like the forms I have still have the following mixed content issues I think. Site is showing secure at least.