This is some deep package interaction, the stuff that is a nightmare to debug. You use both hyperref and cleveref. cleveref uses the following code to define the \cref@addtoreset macro:
\let\if@cref@hyperrefloaded\iffalse%
\global\let\cref@addtoreset\@addtoreset%
\@ifpackageloaded{hyperref}{%
\@ifpackagewith{hyperref}{implicit=false}{%
\let\if@cref@hyperrefloaded\iftrue%
\PackageWarning{cleveref}{hyperref package loaded with
implicit=false option - disabling cleveref's hyperref support.
This situation is not supported by cleveref, and there's no guarantee
anything will work. You're on your own!}%
}{%
\let\if@cref@hyperrefloaded\iftrue%
\PackageInfo{cleveref}{`hyperref' support loaded}%
\let\cref@addtoreset\HyOrg@addtoreset%
Important line is this one:
\let\cref@addtoreset\HyOrg@addtoreset%
When you insert \show\HyOrg@addtoreset at that place, you can see that it is undefined. The reason for that is that hyperref package exit its loading early when it detect tex4ht, before \HyOrg@addtoreset is defined.
To fix that, we need to patch the package loading mechanism in TeX4ht and define \HyOrg@addtoreset before it is loaded. Package fixes are included in usepackage.4ht. The fix can look like this:
\def\:temp{cleveref}\ifx \@currname\:temp
\let\HyOrg@addtoreset\@addtoreset
\fi
The full usepackage.4ht file:
% usepackage.4ht (2020-04-15-14:52), generated from tex4ht-4ht.tex
% Copyright 2003-2009 Eitan M. Gurari
% Copyright 2009-2020 TeX Users Group
%
% 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 latest version of this license is in
% http://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions
% of LaTeX version 2005/12/01 or later.
%
% This work has the LPPL maintenance status "maintained".
%
% The Current Maintainer of this work
% is the TeX4ht Project <http://tug.org/tex4ht>.
%
% If you modify this program, changing the
% version identification would be appreciated.
\immediate\write-1{version 2020-04-15-14:52}
\def\:temp{tex4ht}\ifx \:temp\@currname
\:warning{\string\usepackage{tex4ht} again?}
\def\:temp#1htex4ht.def,tex4ht.sty#2!*?: {\def\:temp{#2}}
\expandafter\:temp \@filelist htex4ht.def,tex4ht.sty!*?: %
\ifx \:temp\empty \else
\:warning{if
\string\RequirePackage[tex4ht]{hyperref} or
\string\usepackage[tex4ht]{hyperref} was
used try instead, repectively,
\string\RequirePackage{hyperref} or
\string\usepackage{hyperref}}
\fi
\fi
\gdef\a:usepackage{\use:package xr,xr-hyper,eso-pic,showframe,expl3,savetrees,cleveref,biblatex,xeCJK,polyglossia,fontspec,tikz,pdfbase,caption,graphics,xcolor,imakeidx,minted,fancyhdr,,!*?: }
\gdef\use:package#1,{%
\if :#1:\def\:temp##1!*?: {}\else
\def\:temp{#1}\ifx \@currname\:temp
\def\:temp##1!*?: {\input usepackage.4ht }%
\else \let\:temp=\use:package \fi
\fi \:temp}
\def\:temp{xr}\ifx \@currname\:temp
\:AtEndOfPackage{\let\XR:\XR@
\def\XR@[#1]#2{%
\Configure{AtBeginDocument}{\XR:[#1]{#2}}{}}%
}
\fi
\def\:temp{cleveref}\ifx \@currname\:temp
\let\HyOrg@addtoreset\@addtoreset
\fi
\def\:temp{xr-hyper}\ifx \@currname\:temp
\:AtEndOfPackage{\let\XR:\XR@
\def\XR@[#1][#2]#3{%
\AtBeginDocument{\XR:[#1][#2]{#3}}
}%
}
\fi
\def\:temp{eso-pic}\ifx \@currname\:temp
\:dontusepackage{eso-pic}
\newcommand\AddToShipoutPicture{\@ifstar{}{}}
\let\AddToShipoutPictureBG\AddToShipoutPicture
\let\AddToShipoutPictureFG\AddToShipoutPicture
\fi
\def\:temp{showframe}\ifx \@currname\:temp
\:dontusepackage{showframe}
\fi
\def\:temp{expl3}\ifx \@currname\:temp
\ifdefined\XeTeXversion%
\xenunidelblock{Latin-expl3}%
\:AtEndOfPackage{\xeuniuseblock{Latin-expl3}}
\fi
\fi
\def\:temp{savetrees}\ifx \@currname\:temp
\:dontusepackage{savetrees}
\fi
\def\:temp{biblatex}\ifx \@currname\:temp
\:AtEndOfPackage{%
\def\blx@mknoautolang{%
\blx@lbxinput{\blx@languagename}%
{}{}%
}%
\def\blx@lbxinput@iii#1#2{%
\global\csundef{blx@lng@#2}%
\:IfFileExists{#1.lbx}
{\blx@lbxinput@iv{#2}{#1}{language '#2' -> '#1'}}
{\ifcsdef{blx@suffmaptried@#2}
{}
{\blx@warning@noline{%
File '#1.lbx' not found!\MessageBreak
Ignoring mapping '#2' -> '#1'}%
\global\cslet{blx@suffmaptried@#2}\@empty}%
\blx@lbxinput@iv{#2}{#2}{language '#2'}}}
}
\fi
\def\:temp{xeCJK}\ifx \@currname\:temp
\:dontusepackage{xeCJK}
\:AtEndOfPackage{%
\RequirePackage{fontspec}
}
\DeclareDocumentCommand\setCJKmainfont{o m o}{}
\let\setCJKsansfont\setCJKmainfont
\let\setCJKmonofont\setCJKmainfont
\DeclareDocumentCommand\setCJKfamilyfont {m o m }{}
\DeclareDocumentCommand\newCJKfontfamily {o m o m}{\expandafter\gdef\csname #2\endcsname{\relax}}
\DeclareDocumentCommand\xeCJKsetup{m}{}
% }
\AtBeginDocument{%
\xeuniuseblock{CJK}
}
\fi
\def\:temp{polyglossia}\ifx \@currname\:temp
\ExplSyntaxOn
\:AtEndOfPackage{
\cs_set_eq:NN\orig_polyglossia@keys_define_lang:n\polyglossia@keys_define_lang:n
\cs_set_protected:Npn \polyglossia@keys_define_lang:n #1 {
\orig_polyglossia@keys_define_lang:n{#1}
\keys_define:nn {polyglossia}{
#1 / direction
. code:n = {}
}
}
\def\RequireBidi{}%
}
\ExplSyntaxOff
\fi
\def\:temp{fontspec}\ifx \@currname\:temp
\ifdefined\fontspec
\:dontusepackage{fontspec}
\else
\input usepackage-fontspec.4ht
\fi
\fi
\def\:temp{tikz}\ifx \@currname\:temp
\:AtEndOfPackage{%
\let\use:tikzlibrary\usetikzlibrary
\def\find:externalize#1external#2\@nil{%
\if\relax#2\relax\else
\let\tikz:externalize\tikzexternalize
\renewcommand\tikzexternalize[1][]{\tikz:externalize[##1,mode=only graphics]}
\tikzset{%
tex4ht inc/.style={%
/pgf/images/include external/.code={%
\includegraphics[]{####1.pdf}%
}%
}
}
\tikzset{tex4ht inc}
\fi
}
\append:defI\use@@tikzlibrary{\find:externalize##1external\@nil}%
}
\fi
\def\:temp{pdfbase}\ifx\@currname\:temp
\:AtEndOfPackage{%
\let\old:outputpage\@outputpage
\def\@outputpage{\old:outputpage{}}
}
\fi
\def\:temp{caption}\ifx\@currname\:temp
\:AtEndOfPackage{%
\long\def\caption@If@Package@Loaded#1[#2]#3#4{}
}
\fi
\def\:temp{graphics}\ifx\@currname\:temp
\ifdefined\XeTeXversion
\PassOptionsToPackage{dvips}{graphics}
\fi
\fi
\def\:temp{xcolor}\ifx\@currname\:temp
\ifdefined\XeTeXversion
\PassOptionsToPackage{dvips}{xcolor}
\fi
\fi
\def\:temp{imakeidx}\ifx\@currname\:temp
\PassOptionsToPackage{noautomatic}{imakeidx}
\fi
\def\:temp{minted}\ifx\@currname\:temp
\:AtEndOfPackage{%
\define@booleankey{minted@opt@g}{breaklines}{}{}{}%
}
\fi
\def\:temp{fancyhdr}\ifx\@currname\:temp
\:AtEndOfPackage{%
\def\ps@fancy{}%
}
\fi
\endinput
Your sample now compiles without errors.
I will update TeX4ht sources to include this fix, so it should be available in TL 2020 soon.
amsthmnow? – Yai0Phah Jun 29 '21 at 11:35