Can you make a custom gutenberg block that allows the gutenberg editor within it?

Shucks, no sooner than the second I desperately resort to asking here, I run into the answer. So for anyone else who just wants a straight answer and not some 45 minute video that never gets to the point…

acf_register_block_type( array(
    'title'         => __( 'Wrapper', 'client_textdomain' ),
    'name'          => 'wrapper',
    'render_template'   => 'partials/blocks/wrapper.php',
    'mode'          => 'preview',
    'supports'      => [
        'jsx'           => true, // this is the line that makes it work
    ]
));

That supports jsx line allows you to assign ACF fields to the wrapper and then the user can gutenberg all they want inside it.

Your custom block’s html needs this in it as well:

<InnerBlocks />

That will enable the gutenberg interface when adding your block in the editor.