After testing the default WP export/import function and numerous plugins, we found one that actually works.

Specs:
RPi 3B+
IIAB 6.7 from today
Raspbian from Oct.

Steps

1. On Box 1 install "All-in-One WP Migration" plugin: https://wordpress.org/plugins/all-in-one-wp-migration/
2. Run it and export file to downloads.
3. Copy file from downloads to flash drive.
4. On Box 2 install WP. Site name, and username/password can be anything.
5. Install "All-in-One WP Migration" on Box 2.
6. On Box 2, change both upload max and post max to 256MB in php.ini (or to whatever your file size is). The plugin max is ~500MB.
7. Upload File from flash drive through the plugin.
8. Log into WP with credentials from Box 1.
9. Profit

I can fill in more details when I replicate this tomorrow.

It would be great to increase upload and post max file size limits to 500MB in local_vars.yml, (apache_high_php_limits: True) or give a space to modify the specific number according to peoples' requirements. Otherwise users will have to modify php.ini (/etc/php/7.x/apache2/php.ini) to their needs for each box.