It is true that html notes are not exporting to a book. Translating them into LaTeX is not possible. The Generations Book extension, however, does have a fix. You just need to provide alternate text or LaTeX content for a book.
To see how, use Extensions->Documentation... menu command and pick "Reports:-= Create Generations Book" from the pop-up menu at the top-right of the documentation menu. Then, click on "Book Optimization" and click "HTML Content Notes" for all the details. This feature was recently improved for the new Internal Scripting version in the extension. There is even a hidden option to quickly test your notes conversions.
I used it for one of my books. My html notes were tables from census records. For the book, I created a LaTeX table. Hint: if you don't know LaTeX well, ChatGPT can give a template for a table. Here is what it gave me
\begin{table}
\centering
\begin{tabular}{lcr}
Left & Center & Right \\
a & b & c \\
1 & 2 & 3
\end{tabular}
\caption{A simple table}
\label{tab:simple}
\end{table}
and ChatGPT followed this template with some explanations.