Quite similar to that Firefox search are Plugins for Wordpress sites here

https://wordpress.org/plugins/

Quite interesting to browse

+ would be good to have this kind of plugin-and-play with unified search and for everything/many more things

Another one with SUPER user reviews and comparisons
https://alternativeto.net/

I guess I'm collecting now for a mega-list of search engines related to finding blockers or freedom stuff!

#freesoftware #floss #foss