user224 , 11 months ago

I have a different idea that wouldn’t require root nor any special setup. Unfortunately, or rather fortunately in this case, I have no way to test it.

My idea:

1. Install Android proxy server from (unfortunately) Play Store
2. Start hotspot on the other device
3. Connect your phone to the hotspot
4. Find your IP address on the network you just connected to (the hotspot on other device) - it should be in WiFi settings, when you click on more details on the connection. Alternatively you could find it in output of ip a in Termux.
5. Open Android Proxy Server app and optionally adjust settings to your liking. (IP address to bind to - should be your phone’s on the hotspot, port, authentication)
6. Enable the proxy server that you want to use. If you’re connected through VPN, it will go through it. I use HTTP/HTTPS proxy.
7. Connect to the proxy server on your other device using your phone’s IP and the appropriate port. In Firefox go to settings, scroll down, click on network setup.

I use this to circumvent the 1 device limit of free ProtonVPN. Also on school network (with authentication enabled) to go through VPN and use NextDNS.