I do think there is an issue with the configuration or my server setup. My server is also running some proprietary software that makes a lot of network configuration changes that I was concerned was interfering with getting https set up (and also the reason I needed to run my dashboard on a separate port).
To test this out, I setup Checkmk on a raspberrypi, created a self-signed ssl certificate, and followed the checkmk documentation for https configuration. It worked with no issues.