I remember reading somewhere about a self hosted application that would work like a proxy. But not http/https like NPM but all the network traffic.
I may be misremembering but what caught my attention at the time was the possibility to log communication packets. It was months ago and I ended up forgetting about it.
My use case would be monitoring communication with a device I’m developing an app for.
Nginx can do that itself with TCP and UDP streams: https://docs.nginx.com/nginx/admin-guide/load-balancer/tcp-udp-load-balancer/
But if you want to analyze traffic, use Wireshark.