People ragging on the only viable browser solution we have... Firefox is rock solid, fast, tweakable, and keeps me as safe as any browser and my configs/habits can. I don't care if management eats babies.
I use it on debian with celenity phoenix and a few about:config tweaks, also tweak'd the theme a bit. Extensions: ublock origin, sponsorblock, localcdn, consent-o-matic, containers, keepassxc-browser, and sometimes jshelter.
web browsing: solved
If I'm not mistaken then Chrome enabled Site isolation in 2019 and Firefox in 2021[1].
MV3 itself is controversial[2] as it unfairly targets extensions that block ad - a major source of revenue for Alphabet.
Alphabet has all the money in the world to make a browser as secure and as privacy friendly as possible. Their focus is only on "secure browser" part.
Mozilla lacks of funding (in compare to Alphabet), but still mostly outdo Alphabet on the "privacy" aspect of browser. And, they play catching up game on security aspect of browser.