The "easiest" way is to switch most or all web browsing to LibreWolf, which is an independent fork of Firefox, better tweaked for privacy. It's not perfect but very close, and no browser is perfect.
The reason why I say that switching to another browser is the easier way to protect from ads (and improve privacy), is because every "standard" browser nowadays is a privacy nightmare, and that includes the standard installation of Firefox, which sends lots of telemetry back to its developers - they even threatened to start blocking websites through the browser "for peoples' safety".
Oh, the atrocities and democides committed throughout history (and today) in the name of "caring and protecting peoples' health and safety".
https://librewolf.net/