None, it is not possible to avoid the_content filter for what you’re trying to do. The only foolproof method is to analyse the final HTML that’s presented.
Page builders rely on different mechanisms to intercept how WordPress presents the content and without knowing how those page builders work you can only rely on the final result for full analysis.
The closest to an official framework or API for this in WordPress is blocks, but page builders don’t use blocks internally, and blocks themselves can be dynamic PHP rendered. You also have non-block non-page builder functionality such as widgets and shortcodes, as well as filters that add content.
This leads me to the question of whether anybody knows of a different way for reading post- and page-content across all possible builder-plugins without using a specific request for each page-builder.
The only way to do this is to render the page as if you’re a user. Either by making a HTTP request, or by using the_content filter.