The only way to achieve webarchive to html conversion, i.e. saving of static websites saved in Safari web archive, is to open the .webarchive in Safari. This will open the web page so you can save it as .html files.
Convert Apple Safari web archive to HyperText Markup Language web page.
We have found 2 software records in our database eligible for .webarchive to .html file format conversion.
Microsoft Windows software - convert webarchive to html on Windows
An easy to use, multiplatform web browser developed by Apple
Convert from webarchive file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned webarchive to html. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert webarchive to html on OS X
A default web browser integrated to Apple Mac OS X