I’m not 100% sure about this, but…
I think you still might need Stunnel to create the Secure HTTPS layer to Blue Iris.
However, you might be able to use the default Certificates that come with Stunnel ??? It’s been a while since I originally installed it and I can’t recall what was “inside” those stock pem files.
Or perhaps there are how-to’s here at Stunnel: stunnel: Documentation