Greasy Fork is available in English.
Change font, size, width and background of a work + blacklist: hide works that contain certains tags or text, have too many tags/fandoms/relations/chapters/words and other options + fullscreen reading mode + bookmarks: save the position you stopped reading a fic + number of words for each chapter and estimated reading time
< Feedback on AO3: Fic's Style, Blacklist, Bookmarks
NEVERMIND it was the fault of something else I was running; it works perfectly!!!
I really love this extension, and it works well for mobile browsing in general! although sometimes, I have to turn it off to open the AO3 filters; the Filter button just doesn't work when I click on it.