Technically, both Chrome and Firefox are adware too, since Google's main business is ads, and Firefox/Mozilla get a lot of money from Google to display Google as a search engine in Firefox (an ad :) )
Firefox doesn't sell BATs, in-browser notification ads, or new tab takeovers. The closest you can get is a pinned site in the new tab page (new installs only) and ads in Pocket, or whatever they're calling that new tab thing these days.
Calling Firefox adware is a stretch at best, and disingenuous at worst. Adware doesn't mean that the software survives because of one advertisement that that user can turn off.
Looks like I'm getting a ProtonMail ad every few new tabs. I never noticed because I've never looked at the new tab page. Doesn't noticeably slow it down to have the ad there, luckily.
I love how quickly the goalpost moves from "No ads" to "Only opt in ads" to "Ads can be disabled with two clicks."
Quit coping and just admit it, Brave is adware. If you like it, that's cool, totally your choice. It's fast, performant adware. But it's adware all the same.
When we're talking about reasons to switch browsers, then saying they both have the same behavior is not whataboutism. It's extremely important context to the complaint.