@Giga_Vril_Breaker @pepsi_man @KarlDahl @sickburnbro The simple answer is it should be "There have been."
The complicated answer is digging deep back to English class, so bear with me.
We can break the sentence down thusly:
"{There} [have been] <a lot> (of rumors) (about the Helene response)"
The basic sentence is "{There} [have been] <a lot>". Both "of rumors" and "about the Helene response" are prepositional phrases. They add detail or clarify what specifically you're talking about in the sentence, but they do not factor into the core sentence.
The subject of the sentence is {There}, but it's a pronoun/dummy subject (apparently what it's called) that substitutes for the actual subject <a lot.> Because <a lot> is plural, the verb takes the plural form of [have been].
Again, this is pulling from English class many years ago (and a little googlefu today) for the explanation but tl;dr it should be "There have been."