How to block posts about Elon Musk (or other custom string) on computer

Using uBlock Origin, you can add your own filter. This filter will block any post with the text "Elon Musk" (not case sensitive), modify as needed.

lemmy.world##div.post-listing:has(span:has-text("/elon musk/i"))

div.post-listing is the element to block
:has(args) returns elements where args evaluate to true
span is the element with the title text
:has-text(needle) returns the element if it has the next needle, supports regex with \needle\ and remove case sensitivity with i

Read more here: https://github.com/gorhill/uBlock/wiki/Procedural-cosmetic-filters