Essentially you stack up several proxies as a chain wesulting in one proxy. Now, if your app has proxy settings, you are done here. If not, you need an app that utilizes Android's VPN api to route traffic from the whole user or specific apps through that 'VPN' app which will route traffic to the proxy. You can use something like Proxy My Apps for that VPN, and need to setup wireguard to expose a proxy.
Depending on your paranoia level, you need to consider the factors I mentioned or more; at the minimum, DNS leak and EDNS metadata leak must be considerered. There might be other de-anonymizing leaks in this stack however if your adversary is just websites, CDNs and DNS; you should be fine if you use something like Tor browser while respecting opsec principles.
The integrated solution to that is Android's VPN api. It is what you use to route apps through tunnels of your choice. You need an app that utilizes that api in the way I described.
You could set this stack on each user and due to Android's security model they'll each have their own independent VPN.
If you find an app to stack proxies like 3proxy, you could use that rather than Termux+3proxy that's used to chain the proxies and expose the tunnel as a single proxy.