Hide the isekai general on /a/ recognizable by its OP post containing the word isekai in spoiler.
Violentmonkey, Tampermonkey, or Greasemonkey along with 4chan-X is required.
The script listens to the 4chanX API calls and hides the thread(s) that contain the word isekai (or whatever you have replaced it with) in their post message when all posts have finished rendering (when PostsInserted event happens).
You can read the script if you want a more through explanation.