FYI, your post title should use “whoever”, not “whomever”.
A good trick to tell whether to use “who” or “whom” is to replace “whom” with “him” or “who” with “he”. It’ll be immediately obvious (to a native English speaker) which is correct.
Whomever invented LED bus advertisements becomes Him invented LED bus advertisements
Vs
Whoever invented some stupid shit becomes He invented some stupid shit
FYI, your post title should use “whoever”, not “whomever”.
A good trick to tell whether to use “who” or “whom” is to replace “whom” with “him” or “who” with “he”. It’ll be immediately obvious (to a native English speaker) which is correct.
Whomever invented LED bus advertisements becomes Him invented LED bus advertisements
Vs
Whoever invented some stupid shit becomes He invented some stupid shit
It says “to”. To whom.