Activate SSL/Replace Web Server Certificate

I’m new to this community and also quite new to Foreman. Therefore, I would like to thank you in advance for your patience and help.

Problem:
We’re using Foreman (with Katello) and we would like to replace the certificate (so that our administrators do not get a certificate warning).

I’ve started with this guide: Foreman :: Replacing Foreman’s web SSL certificate. and ended up trying out different settings in various files. None of that worked.

The certificate seems to be ignored and it seems like I do not receive any error at all.

Expected outcome:
https://foreman… should get accessible without certificate warning.

Foreman and Proxy versions:
Foreman: 1.18.3

Please let me know if you need more information (or settings from specific files).
Many thanks in advance!

As far as I remember @Gwmngilfen wanted to write a newer guide for Foreman (or at least we talked about last Cfgmgmtcamp) as the one you linked is quite old.
But for Katello it gets more complicated, in the one environment we use a sub-CA from the companies CA for the complete Katello infrastructure to solve this. Starting with this is not so difficult, but changing afterwards is really a challenge.