The correct option is https_proxy.

GitHub Actions runners establish outbound connections to GitHub over HTTPS and the runner reads the lowercase proxy environment variables for its network configuration. Setting this variable directs all HTTPS requests through your HTTP proxy so registration and job dispatch can succeed in a restricted VPC.

NO_PROXY defines hosts that should bypass a proxy and it does not tell the runner which proxy to use, so it will not enable connectivity by itself.

HTTP_PROXY applies to plain HTTP traffic and the runner connects to GitHub using HTTPS. The runner also expects the lowercase names for proxy variables, so this one is not used.

network_proxy is not a standard proxy environment variable recognized by the runner or common networking libraries, so it will be ignored.

Full AWS Practitioner Certification Question