During the 10/1/2021 John Mueller hangout, one webmaster asked about on-site search results and whether or not they should allow them to be indexed.
John explained that one should use noindex on internal site search results pages. Google wants to be able to recognize these pages, and this could be helped by adding a noindex to the pages.
It’s an ideal situation because the alternative would be a bad user experience—sending people to empty search results pages in Google’s SERPs (search results pages).
This conversation happens at approximately the 37:16 mark in the video.