OK,
So I have verified that my LB is passing along the "X-Forwarded-Proto" request to the Web servers. I added in %{X-FORWARDED-PROTO} to the logging section on /app/configurations/conf.d/kaltura.enabled.conf. In the apache access logs, I am seeing the value "https" in the header of the GET requests.
And certain parts of the site are working, like the landing page and all of the Administration Console.
The problem seems to be the KMC, which is trying to grab things over https, on port 80. For example, when logging in to the KMC:
https://mykaltura.com:80/api_v3/index.php?service=multirequest&action=null&kalsig=81a40dd9a3ff56b3eace73eed3138233
Will continue looking.