guess there is nothing more to do here, closing.

reference and screen shots at

https://tex.stackexchange.com/questions/546249/why-tex4ht-adds-extra-frame-when-table-inside-longtable

===================
\documentclass[11pt]{article}
\usepackage{longtable}
\begin{document}

When table inside long table, it adds extra frame

\begin{longtable}{|p{1.75in}p{1.75in}|}\hline
\begin{tabular}{p{1.75in}}
entry 1
\end{tabular}
&
\begin{tabular}{p{1.75in}}
entry 2
\end{tabular}
\\\hline
\end{longtable}

When table on its own, no extra frame shows up

\begin{tabular}{p{1.75in}}
entry 1
\end{tabular}
\end{document}

========================

Thank you
--Nasser