I wrote a Wordpress to Grav exporter [1], which brings over most content (posts, pages, users, groups, attachments, some site-metadata, etc). I also wrote a Drupal 7 one, but I haven't touched that in a long while.

After exporting from either CMS, it's pretty close to drag/ drop onto the grav instance and everything should "Just Work (tm)".

- [1] https://github.com/jgonyea/wp2grav_exporter - [2] https://www.drupal.org/project/grav_export/