just go to settings > search and either uncheck (to disable) or remove (to remove)

Not sure if there's such a thing as a "good" AI company but I gather this is one that achieved its position via shady practices and is privately funded to serve ultra-wealthy interests.

Perplexity AI has attracted legal scrutiny over allegations of copyright infringement, unauthorized content use, and trademark issues from several major media organizations, including the BBC, Dow Jones, and The New York Times. According to separate analyses by Wired and later Cloudflare, Perplexity uses undisclosed web crawlers with spoofed user-agent strings to scrape the content of news websites who disallow or explicitly block web scraping.

Promoting companies like this is part of the more fundamental issue with Firefox's funding model. The Mozilla Foundation uses Firefox as a cash cow by doing deals with devils (chiefly Google), putting some of the money back into Firefox while the rest goes toward activities the foundation sees as forces for good. You might call that irony or ingenuity, or both, but we're stuck with it absent roughly five million users pitching in 50 bucks every year, at least based on current development costs.

"Advertised" is a peculiar way to say they added a new default search provider.

This is such a huge tempest in a teapot. It's just a shortcut to let you put a query directly into Perplexity, like any other search engine. If you don't want it there go to the search engine configuration menu and remove it, or just ignore it like 99% of people do with the other search engines in that dropdown they don't use. But because the dreaded letters AI are involved and nothing baits the rage like those letters these days there's headline after headline about this ridiculously trivial thing.

Guess what? Along with Google, they're all Mozilla partners!

Ah yes, AI magical doohicky thing