List of free proxy stuff for developerππ½
If you're looking for all programming tools around proxy (not just free). Check this page List of proxy Programming Tools

Loophole
Instant hosting, right from your local machine. It's totally free and excellent alternative to ngrok
Tag: proxy, local-server, tunnel
Traefik Labs: Proxy
Traefik is the leading open-source reverse proxy and load balancer for HTTP and TCP-based applications that is easy, dynamic and full-featured.
Tag: https, proxy
check it out at https://traefik.io/pricing/

ngrok
ngrok is the fastest way to put anything on the internet with a single command.
Tag: proxy, local-server, tunnel
Ephemeral/Random Domains Serve HTTP Apps, Webhooks, APIs, and TCP-based systems Automated SSL/TLS certificates Request Inspection & Replay APIs and Terraform Provider Restricted bandwidth and usage
Localtunnel
Free local server to public internet tunnel. Ngrok alternative. Expose yourself to the world
Tag: proxy, local-server, tunnel