Qwant is a OpenSearch search engine. Go to the Qwant search site and you can then add it to the search bar by clicking on magnifying glass icon in the Search bar and then Add search engine "Qwant".

https://support.mozilla.org/en-US/kb/add-or-remove-search-engine-firefox

There are also lots of Qwant search engine options on https://mycroftproject.com/search-engines.html?name=Qwant

Thank you, James.

It is fine that it is possible to make Qwant the default search engine. However, this in my opinion is not enough. Currently, in the search engine selection drop-down the only options I have are Google, Bing, DuckDuckGo and Wikipedia.

Mozilla should help promote open source by at least making Qwant an option in the drop-down. This might encourage some users to try it. The installation process you outlined is difficult, and only useful to people who already know about Qwant and desperately want to have it!

They are on the list in some countries, at least in France.