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!
Decentraleyes … Nice! Never seen that one! I always suspected hosted libraries and the such come at a costs (like jQuery etc…).
Decentraleyes was good but has been unmaintained for quite some time, I believe LocalCDN is the current replacement.