> This. I don't even want my computer to send data / check email unless I tell it to. And I ESPECIALLY don't want it sending telemetry / receiving ads asynchronously.

This should be the job of the OS, but ironically the OS is the biggest offender.

Should be solvable by a strong firewall/local proxy that blocks everything by default, only allows browser, and has an easy and convenient way to allow some outgoing traffic temporarily.