\RequirePackage{pdfmanagement-testphase}
\DeclareDocumentMetadata{pdfversion=2.0,uncompress}
\documentclass{article}
\usepackage{luamml}
\usepackage{tagpdf}
\tagpdfsetup{
activate-all,%paratagging,
interwordspace=true,
}
\usepackage{amsmath}
\begin{document}
\ExplSyntaxOn
\luamml_flag_structelem:
\ExplSyntaxOff
\tracingmathml=2
\tagstructbegin{tag=Document}
\begin{align}
ax^2+bx+c=0 =\sqrt{4}
\end{align}
% \[ a=b\] %errors
\tagstructend
\end{document}