Useful information to include:

• Minecraft version
• 1.16
• CC: Tweaked version
• 1.95.1
• Logs: These will be located in the logs/ directory of your Minecraft instance. Please upload them as a gist or directly into this editor.
• Detailed reproduction steps:
  whitelist local domains in the http config section and request one using http.get
  it will give the domain not permitted error

additional information:
I am trying to request files from a local git instance (which isnt working for other reasons i have yet to figure out gives a could not connect error)
After problems with this I tried requesting other internally available addresses namely a pihole page and a homeassistant page. these both give the domain not permitted message.

I did verify in mc 1.12.2 with cc:tweaked 1.89.2 and both the pihole and homeassistant requests work. This leads me to believe the config file in 1.16 is broken.

what i have tried:
removing the http.rules section that deals with the $private domain in world/serverconfig
changing the action to allow

Works for me :).

for some reason after restarting minecraft a couple of times it works i have no idea why.
i am assuming but i have no way to proof it is that for some reason minecraft doesnt reload configs when you enter a world again. and you need to close it completely to get it to work.

sorry for the bad report.