Depends on the software you use. There’s also Linux software suspected to send data home. And there’s also closed source commercial Linux software.
If you want to investigate what your computer really does have a look at the logs of your wifi router. Most routers (allow to) store all outgoing HTTP requests and provide a nice ordered log file.
As long as no better knowledge is proved I would assume that every access on such servers is stored somewhere. You can’t control it. That’s why it’s not good to come a second time with the same IP and other unique properties.
Thank you! I forgot also to ask about OCSP in browsers. Do you know anything about that? If i use VPN does it matter if the browser uses OCSP? I heard it could hurt privacy.
Generally hardware doesn’t call home, however drivers might do. You’re pretty safe using open source drivers on Linux I think. However, on Intel systems there still is the Intel Management Engine (IME) that’s kinda problematic. We know it got universal access and can be accessed via network even when the device is off, so it’s expected to include the backdoor Snowden talked us about (in case you know the movie: The one used to access the webcam without starting the Mac). Technically, there could be anything in there, we just don’t know. Same goes for AMDs Platform Security Processor (PSP), however that one doesn’t have access to the NIC and shouldn’t be accessible when the device is powered down.
Unfortunately, we also don’t know enough about all of this and there’s nothing we can do about it either, any speculation about it quickly becomes a slippery slope towards conspiracy theories.