It may be frustrating for many people who got an error message:
ifpdf[2019/10/25 v3.4 ifpdf legacy package. Use iftex instead.]
Don't panic or go crazy... Let me do probably the dirtiest fix you probably ever heard of, while waiting for someone to come up do an official fix.
Locate your MikTex folder, for example, something like:
C:\MiKTeX\tex\generic\iftex
Modify the file ifpdf.sty:
% Compatibility stub package for ifpdf
%% LaTeX3 Project
%%
%% This work may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either
%% version 1.3c of this license or (at your option) any later
%% version.
% The original ifpdf package was written by Heiko Oberdiek
\ifx\RequirePackage\undefined
\input iftex.sty
\else
%\ProvidesPackage{ifpdf}[2019/10/25 v3.4 ifpdf legacy package. Use iftex instead.]
%\RequirePackage{iftex}
\input iftex.sty % The above two lines commented out, so the effect is equivalent to \input iftex.sty and do nothing else, no need to check.
%But I want to keep the changes minimal withour deleting anything. -- Comment made by MathWit.com
\fi