I may have missed a previous question here, because the site ignores "either" and "or" when searching for "either" or "or".
But searching "term1" (term2 OR term3) just gets a red search bar and ignores term2 and term3. And searching "term1" (term2|term3), as suggested here
https://manual.calibre-ebook.com/regexp.html , also gets a red search bar and ignores term2 and term3.