There are several existing options:

- Windows: Simplewall (uses native WPF for filtering), Portmaster (interactive firewall, uses custom kernel extension).

- macOS: LuLu or Little Snitch (they all use a native filtering API, which unfortunately is not perfect: https://lapcatsoftware.com/articles/2023/6/3.html).

- Linux: OpenSnitch, denying network permission to Flatpak apps.

- Android: Rethink, NetGuard; GrapheneOS has app network permission natively.

iOS is the only OS where no application firewall is available, although if you don't use Wi-Fi, you can block apps from using cellular data.