Just don't connect your ereader to the internet. Before I switched, I stopped letting my Kindle reach the internet because every automatic update made the UI worse than it was before.
Either keep it permanently in offline mode (which you should anyways to save on battery power) or segment it out on your network if you need wifi for something local.
Load books locally via calibre and USB.
I rooted my $99 Kindle so I wouldn't have ads or spyware, best decision ever. Lets you do custom screensavers and run ePub readers.
I didn't even know calibre connected to the internet.
I haven't messed with it in awhile but I recall either the main devs or a plugin testing wireless syncing. It would definitely be convenient but then you have to do some networking setup on the backend.
Edit: oh yeah calibre connects to the internet for ebook meta data and cover downloads.
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