In theory you could also use PHP as a pre-processor; install it locally, copy the sources to the webserver root, then use wget --mirror to extract a post-processed version of the site.

You'd still need PHP installed on your home machine, but then again, it's not like you don't have to install some pre-processor anyway.

> use wget --mirror to extract a post-processed version of the site.

or just use php file.php > file.html

Sure, but you'd need to process each file, or write a script to do it, when wget --mirror fetches the whole site at once.

and by plain HTML, you mean plain Python installed and configured on your server/local

The server doesnt need to have Python installed. Just your local machine. That is a simple one liner if it isnt already installed.