Mandatory:

• Dark Reader for dark mode anywhere, and Invert Colors for the occasions when a site is not usable with Dark Reader.
• Ublock Origin of course, but I also still use uMatrix because even several years after it stopped being maintained, it's STILL unmatched by any other addon in the content-blocker category. The granularity of being able to specifically allow scripts or frames or images or cookies from specific third-party domains or subdomains either everywhere or only on certain first-party domains, with a very intuitive visual grid (matrix) and subdomain selection, is incredible. I still don't understand why it's deprecated.
• Tree Style Tab and the related Tab Unloader. I forget things exist if they aren't right in front of me, so if I have any intention of coming back to a site or a workflow, I need those tabs somewhere in front of me, tucked away in a tree waiting for me to get back to them. I regularly have between 100-200 tabs open. Being able to unload performance-heavy tabs without restarting the whole browser also helps a lot.
• Bitwarden because if you aren't using some kind of password manager, do you even care about security?
• Translate Web Pages because not everything I want to read is in English

Nice to haves:

• Tranquility Reader, because the browser's built-in Reader View often shits itself and doesn't work, particularly on social media text posts. This lets me select the page contents I want it to grab in case the automated picker fails. It's still a bit janky though; if anyone has a more polished alternative, I'd like to hear about it!
• Enhancer For YouTube, Sponsorblock, and Return YouTube Dislike
• stutter For when I feel like speed-reading
• Toolbox for Google Play Store