Ublock Origin is an obvious one, but I also can’t stand not having Foxy Gestures anymore. It adds customizable mouse gestures, so you can set it up to have easy swipes to go back a page, reload a page, close a tab, etc, and it feels wonderful and smooth to use compared to just using the traditional buttons to do everything. Honestly it’s kinda wild to me that this isn’t more popular now that people are so used to phone gestures. It’s good for the same reasons!
You can use dark reader and stylus (firefox extensions).
I use stylus to ‘correct dark reader’ or if i want write own style, or to change few elements on website.
I don’t remember how, but in dark reader in settings you can define your colors (background etc.), you can even set font! I use for example nerd font “CodeNewRoman NF” it works.