As this thread discusses, lualatex has some problems with T1 fontenc.
On the other hand, without T1 fontenc
\documentclass{article}
% \usepackage[T1]{fontenc}
\begin{document}
"\dots"
``\ldots''
\end{document}
lualatex uses the "horizontal ellipsis" character of unicode for \dots and the "right double quotation mark" character of unicode for the " input. Neither of them is optimal: The unicode ellipsis character is often too narrow and you sometimes want the straight double quotation symbol. (If I want the proper closing double quotation mark, I would write '' or use \enquote{}, thank you very much.)
So, how does one redefine \dots (and \ldots) and " without using T1 fontenc?
(Why do I want to use " ? Because I'm quoting a lot of other people's text copy-n-pasting from email. I want to minimize editing the quoted text.)
EDIT: Solution to the \ldots problem: \usepackage{ellipsis}.
Apparently, the ellipsis package has to be loaded after the hyperref package. Perhaps hyperref redifines \dots to use the unicode ellipsis. Strangely, this redefinition doesn't happen with pdflatex, with or without T1 fontenc. Nor does it happen with lualatex with T1 fontenc.(That's why it was so hard to figure out what was going on.)
\renewcommand\ldots{.\kern.3em.\kern.3em.}or whatever spacing you would like. – David Carlisle Jul 18 '20 at 09:23\dotswith a more traditional definition. Therefore you certainly can change the width that way and it seems to do exactly what you want. – Marcel Krüger Jul 18 '20 at 13:30\ldotsto be substituted with the unicode ellipsis and fix my original posting. – Ryo Jul 19 '20 at 13:29\dotscommand to produce the unicode character "horizontal ellipsis". – Ryo Jul 19 '20 at 13:56