Debian is a stable server distro, but in the desktop space users expect everything to just work and while Fedora is usually backwards compatible, Debian isn't always forwards compatible.
As for security updates, IDK.
I'm operating mostly of second-hand information I vaguely remember, I'm not an expert on these things so I'm not really the person to be discussing this with. There's surely a reason Linus uses Fedora over Debian though.
I should've known that but forgot. You're right, my ISP shouldn't be able to see anything but that I visited Wikipedia. They wouldn't know that I searched for rambutan.
I have Freetube installed but I found no reason to really use it when I have this browser extension and adblock (though I don't have one enabled for YouTube so I have no idea why I'm not seeing ads). I can probably do what Remove YouTube Suggestions does with Tampermonkey or Violentmonkey anyway so I might switch.
Didn't realize Tampermonkey wasn't open source. I'll look into it when I can eventually be bothered.
I can't use a Passkey on my phone. GrapheneOS doesn't support passkeys.
Piracy isn't worth the hassle to me, though it's not like Crunchyroll has been much better lately.
Firefox only stores the time of my most recent visit so I don't have that information anymore, so let's just assume I went to YouTube immediately afterwards.
If my exit point is my ISP, and my ISP is selling my data to advertisers (hypothetically), then a VPN would make a difference. That's why I mentioned it.
I use AdGuard rather than uBlock Origin for adblocking, because it allows me to opt-in and only block ads when they are aggressive enough to be annoying. But I've not been trying to minimize fingerprinting. The issue is just that everything I used in this instance came with either a tacit or explicit promise not to track me and I don't know which is lying.
Other extensions I use are:
Remove YouTube Suggestions
10ten Japanese Reader (just now disabled)
Tampermonkey
Proton Pass (because my government services require 2FA, but only offer an official government app that uses the play integrity API, or a Passkey which is only natively supported on Windows or Mac)
Time Tracker - Web Habit Builder
Improve Crunchyroll (which seems to have stopped Crunchyroll from forcefully dropping my resolution to 144p).
Apparently Startpage and Duckduckgo use contextual advertising (rather than targeted advertising) so the advertisers on an unrelated website shouldn't know I was looking up rambutan.
Looking it up my ISP isn't exactly trustworthy, but there have been no clear allegations. I'd say it's the most likely cause if not my Firefox extensions.
Why do people use PopOS? I genuinely don't get it.