Where is that line for you? Is occasionally checking for security updates strictly necessary? Is reporting a crash to the devs so they can fix it necessary? What about sending system & usage telemetry so they can prevent future bugs?
For me, it's like GP said: Absolutely no unauthorized network traffic unless strictly required for the purpose of the software (e.g. curl). No security updates, crash reporting, telemetry unless you prompt the user and show the user exactly what will be sent (similar to how syncthing does it).
Anything less is voyeurism.*
* extreme language I know, but it's precisely how I feel about these acts.