Just like you can change your Windows PC to Linux, or install a custom ROM on Android, to have better control over your devices, it is also possible to change the firmware on most routers.

OpenWRT is the most popular option for that. It’s a Linux based firmware, that has a package manager allowing you to install additional things on your router.

For example, I have a TP-Link TL-WR902AC v3. Out of the box it is just a USB-powered 5GHz extender. After installing OpenWRT to it, I added:

• WireGuard: to route all the traffic over my VPN
• DNS-over-HTTPS: to encrypt all DNS requests
• USBIP: this is because I sometimes use it to connect a webcam for my cat, and I forward the camera to my server in another room

By adding WG and DoH to the “repeater”, I can connect this little guy to any public WiFi, and securely connect my devices to it.

TL;DR: Do not sell the app, sell the service

After reading all the comments, I am a bit confused.

Based on my understanding, this a self-hostable, privacy friendly app, that does not contain a libre license, as you plan on monetizing it.

First of all, the primary reasons of opting for libre software are privacy and freedom. So, the lack of such license can be considered a red flag.

Second, a lot of privacy conscious Android users download their apps from services like F-Droid, that have strict rules against closed-source. So, trying to sell a privacy solution on Play Store does not sound like a good business model.

Tips for monetizing a libre service:

1. The client should have a libre license. You code running on the user’s device should be verifiable.
2. Charge for your STUN/TURN server.
3. Sell the server blob. Sandboxing apps on a Linux system is far easier (to prevent them from accessing the internet and potentially leak data).

There are apps that are even available on F-Droid, and are similarly monetized. Some examples, that I use, are: Bitwarden, Mullvad, Telegram and Tailscale.

I mostly use it for accessing my servers when I leave home. So, no need for constantly updating it. I prefer to install the OS and forget about maintaining it on that device.

I have Debian on a laptop that I don’t use that much, and I use Nix package manager for managing the apps I use.

Running Arch was a nightmare, as I was updating once every 1-2 months and I was getting lots of conflicts.

Have you tried Fennec?