[tex4ht] tex4ht gives amsmath Error: \tag not allowed here

[Nasser M. Abbasi]

I just got this error, only with tex4ht:

-----------------------------------------

(/usr/local/texlive/2018/texmf-dist/tex/latex/amsfonts/umsb.fd)

! Package amsmath Error: \tag not allowed here.

See the amsmath package documentation for explanation.
Type  H <return>  for immediate help.
  ...

l.11 ...thrm{d}y}}{\mathop{\mathrm{d}x}}\right) \tag
                                                   {1A}
?
--------------------

The funny thing, when I went to ask about it at
https://tex.stackexchange.com, it turned out I asked
the same question more than one year ago and forgot:

https://tex.stackexchange.com/questions/383129/tex4ht-gives-package-amsmath-error-tag-not-allowed-here

But there was no resolution on that.

Is this a bug in tex4ht? Should I enter a bug on this? MWE below.

THis compiled OK with lualatex and pdflatex. So I expected it to
compile ok with tex4ht as well.

>cat T.tex

------------------------------
\documentclass[11pt]{book}
\usepackage{amsmath,mathtools,amssymb}

\begin{document}
\[
   y \left( x \right)  = G\left(x, \frac{  \mathop{\mathrm{d}y}}{\mathop{\mathrm{d}x}}\right) \tag{1A}
\]
-----------------------------

compiled with

make4ht -ulm draft
         -f html5+dvisvgm_hashes T.tex 'htm,0,pic-align,notoc*,p-width,svg'

why \tag does not work with tex4ht in \[ \] but works with lualatex?

What is a workaround? comment on the above question says not to use
align for single equation and so I use \[ \] for single equation
but want to tage it also.

thanks
--Nasser