I created my own VPN or proxy server on a rented Ubuntu server. For example it may be an OpenVPN server with Pritunl or a Wireguard server with wg-easy or wg-install or firezone installation script.
In another case, I created a https proxy server with login and password authorization using dumbproxy or a secure socks5 server using shadowsocks, with or without obfuscation.
Let's say I want to use such a server not only for myself, but to provide access to my friends or clients. That being said, I want to limit the access of each of them in such a way that each of them does not take up all the bandwidth alone. That is, apply bandwidth limiting per user.
Of course, I do not know from which global IP address each user comes in and I cannot guarantee that his address will be permanent. While I can expect their VPN address to be constant, I can't expect the same for a proxy server. I could probably limit the connection speed by the IP address in the vpn network for vpn clients, but not for proxy clients.
What should I do? I am not an experienced Linux user and I prefer solutions that are simple and accessible to inexperienced users, such as easily customizable TUI programs or ready-made solutions with a web interface.
Using a proxy server in my case is preferable compared to a VPN server, since it allows users to use it selectively in the right applications.
Perhaps there is a ready-made solution in other implementations of HTTPS proxy servers or in software firewalls or linux distributions for routers?