I was able to configure Netcam Studio for https using a free certificate from Lets Enrypt. I have my own domain registered with no-ip.com (www.ngcard.net) and I set up a sub domain for use by Netcam Studio (ww2.ngcard.net) this uses dynamic DNS through no-ip.com. Up until now this subdomain was running on plain old http, so I was starting to see the mixed content issues with my main site.
To create a Lets Enrypt certificate I followed these instructions to install certbot on my Netcam Studio Server. I also had to make sure I port forwarded port 80 to the server because certbot uses this to prove that you own the server and also will automatically renew the certificate every 3 months. It’s safe to leave port 80 open since it will only be live while certbot is doing it’s thing. I run Netcam Studio on port 8100. Also if you run the Windows Defender Firewall, make sure you allow port 80 traffic for certbot - the certbot installer doesn’t do this for you.
I ran the command certbot certonly --standalone
Running certbot will prompt you for some information including the domain you would like to create a certificate for - I entered ww2.ngcard.net. It will then generate a certificate for you and place it in C:\Certbot\live[certificate_name]. It actually creates several variations. You want to use the one named fullchain.pem.
Since certbot creates pem files you will need to convert it to a pfx. You can do this various ways including online via this site https://www.sslshopper.com/ssl-converter.html.
Once you have your fullchain.pfx file follow the netcam studio directions for importing the certificate into the Windows certificate store and copying to the Netcam Studio folder, and configuring the Netcam Studio configuration files.
Webrowsers are now much happier with my site https://www.ngcard.net/webcams.