I’ve been on Fedora for a few years now, and been using some kind of Linux as primary for over 15 years. Your experience sounds like something from a few years ago.
If you haven’t tried Fedora yet, I’d highly recommend it over Ubuntu, which is likely one of the bigger cause of your issues.
Yes, that is correct. This also excludes self-hosted sites using Jetpack, as well as sites hosted on WP VIP platform.
If you stay on WP.com, there is a new setting(per-site) under Settings > general for disallowing this.