The Multi Account Containers extension has an Advanced proxy settings at the bottom when you go in to Manager Containers. I have a go based socks proxy running on docker somewhere. I enter the details for that there. Syntax is socks://ip:port .
I have two socks implementations installed. I A/B test them sometimes but they seem to be basically equivalent in terms of performance.
https://github.com/net-byte/socks5-server
https://github.com/ocassio/go-socks5-proxy (old but works fine)
Note: If you're using a chromium based browser you can use the excellent SwitchyOmega plugin to do this much easier and with more functionality. No containers of course.
- Proxy SwitchyOmega: https://addons.mozilla.org/en-US/firefox/addon/switchyomega/
- Source: https://github.com/FelisCatus/SwitchyOmega
Another option is the FoxyProxy add-on:
- FoxyProxy Standard: https://addons.mozilla.org/en-US/firefox/addon/foxyproxy-sta...
I am aware of foxyproxy. It works OK. I was using it until the containers gained proxy support.