Please explain ? "Spyware built into browsers and Linux itself". Assuming you mean browsers that seem to respect information safety like Firefox and not Chrome/Chromium. And about the Linux part
for Linux I shouldn't say Linux in general, but Ubuntu
Constant connection attempts to geoip.ubuntu.com.. and lesser attempts to daisy.ubuntu.com, ntp.ubuntu.com, changelogs.ubuntu.com.. ssometimes extras.ubuntu.com, videosearch.ubuntu.com
there's zero reason for it to be connecting to any of those, and that first one in particular sure sounds spy-ish.
I can happily say none of my computers are infected with Chrome .lol. the biggest piece of spyware out there!
And yes FireFox has spyware! Some of which can be disabled, but not through the normal options.
Things called, for example: 'Telemetry', 'Health Report', Pocket', 'Safe Browsing'.
Makes connection attempts to servers like: detectportal.firefox.com, addons.mozilla.org, aus5.mozilla.org (others too, but those I long ago removed in its extended options). The first one listed here IS a spy server.
PaleMoon (a FireFox clone) has some of the same, but not as bad.
I disabled the majority of it long ago, still get connection attempts blocklist.palemoon.org though.
Icedragon (another FireFox clone) has some too, but like PaleMoon not as bad as FireFox.
I disabled the majority of it long ago, but it has one really bad one...attempts to connect to download.comodo.com with every site you visit.
Just a couple of many articles that can be found on FireFox
neocities.org ... firefox github.com ... haasn The top part of that 2nd link is good stuff, though be careful making any of their recommended changes.
And in particular those starting with "security." (same for the addons they list), in general for those I reccommend don't do it!
(some of the listed settings also are in various FireFox clones)
If you change anything, go test the sites you normally use and make sure they still work. Some of the changes will make some sites not work (the "security." and DNT header ones in particular)