Tinyproxy

Server

apt install tinyproxy

minimum config here,

grep "^Allow" /etc/tinyproxy/tinyproxy.conf
Allow 127.0.0.1
Allow 10.10.9.xxx # < This

Clientele

Firefox
https://support.mozilla.org/en-US/kb/connection-settings-firefox

Chrome
Untested, but

google-chrome --proxy-server=host:port

might work.

Debian apt (WSL)
https://dev.to/david_j_eddy/windows-10-wsl-ubuntu-1804-proxy-configuration-for-apt-fhi

Git

git config --global http.proxy http://proxy.server:port