My favourites:

Augmented Steam - Augmented Steam is a browser extension by IsThereAnyDeal that improves your experience on the Steam platform by providing helpful information and tons of customization options.

Bitwarden Password Manager - At home, at work, or on the go, Bitwarden easily secures all your passwords, passkeys, and sensitive information.

ClearURLs - Removes tracking elements from URLs

Dictionary Anywhere - View definitions easily as you browse the web. Double-click any word to view its definition in a small pop-up bubble. It also supports Spanish, German, French language alongside English. Enjoy Reading Uninterrupted!!!

Don’t track me Google - Removes the annoying link-conversion at Google Search / maps / …

Facebook Container - Prevent Facebook from tracking you around the web. The Facebook Container extension for Firefox helps you take control and isolate your web activity from Facebook.

Google Container - Prevent Google from tracking you around the web. The Google Container extension helps you take control and isolate your web activity from Google.

LibRedirect - Redirects YouTube, Twitter, TikTok… requests to alternative privacy friendly frontends.

Sidebery - Vertical tabs tree and bookmarks in sidebar with advanced containers configuration, grouping and many other features.

Startpage - This search engine extension protects users from being tracked while allowing them to search the web in complete privacy. Startpage is a private search engine with no tracking, storing, or selling users’ search history.

Undo Close Tab - Allows you to restore the tab you just closed with a single click—plus it can offer a list of recently closed tabs within a convenient context menu.

uBlock Origin - Finally, an efficient wide-spectrum content blocker. Easy on CPU and memory.