cm4all

ImpEx is a WordPress plugin that allows you to import and export data from and to your WordPress installation.
The primary goal for ImpEx is to provide a true Open Source WordPress Plugin for importing/exporting your WordPress data (including data from third-party plugins/themes).
This plugin is in an early (but working) stage.
Impex provides :
<ul>
<li>
WordPress hooks for third-party plugins to expose their own data to ImpEx Import / Export without being dependent on Impex.
</li>
<li>
a (semi) streaming architecture for large data exports/imports.
</li>
<li>
Definition of configurable import/export profiles defining data providers to use and configuration of these data providers
<ul>
<li>A user interface for importing / exporting data via ImpEx WP admin screen</li>
</ul>
</li>
<li>
the ImpEx API is designed to support resumable/cancelable imports and exports.
</li>
<li>
ImpEx provides a REST API integrated into WordPress
</li>
<li>
ImpEx is explicitly designed for use in managed WordPress instances
</li>
<li>
ImpEx development relies heavily on PHP unit testing its feature set to be stable and consistent.
</li>
<li>
a <a href="https://ionos-wordpress.github.io/cm4all-wp-impex/impex-cli.html" rel="nofollow ugc">CLI</a> for importing/exporting data via ImpEx REST interface. 
The ImpEx CLI can be used as an alternative to the ImpEx WP admin screen.
</li>
<li>
related NPM package <a href="https://www.npmjs.com/package/@cm4all-wp-impex/generator" rel="nofollow ugc">@cm4all-wp-impex/generator</a> enabling transformation of any content to Impex Export format.
Using this package you’re able to convert any content to WordPress and import it using the ImpEx plugin. See the <a href="https://ionos-wordpress.github.io/cm4all-wp-impex/cm4all-wp-impex-generator/static-website-tutorial.html" rel="nofollow ugc">Tutorial</a> 
or <a href="https://www.youtube.com/watch?v=pjG69RmULYo" rel="nofollow ugc">watch the walk-trough at YouTube</a>.
</li>
</ul>
Your help is welcome !!

cm4all-wp-impex

ImpEx contributes extendable Import / Export functionality to WordPress

cm4all-wp-impex vs UpdraftPlus: WP Backup & Migration Plugin