I have OPNsense 20.1.4-amd64 running with os-nginx 1.19 installed and working 100%
Certain HTTPS servers are restricted by IP ACL's, which also works great.
Is there anyway to configure a custom 403 Forbidden page when a HTTP/S requested is rejected based on the IP ACL?
Maybe you can get that done by a custom include but it does not work with the web interface. You can see the include in the generated configuration.
See /usr/local/etc/nginx/nginx.conf