Cover Block with a max-height block style

cover-max-height.php

<?php

// Add to your theme's `functions.php` file.
//
// This block style has limited use cases to where you know 
// what's going to be shown inside the Cover block. Often,
// setting a `max-height` is not a good idea when you have 
// nested variable content.
//
// CSS `min-height` always overrules `max-height`, so this will
// only work if the `min-height` is lower than than the max.
//
// Set the `500px` value to your preferred limit.

add_action('init', function() {
	register_block_style('core/cover', [
		'name'         => 'max-height',
		'label'        => __('Limited Height', 'your-theme-slug'),
		'inline_style' => '.wp-block-cover.is-style-max-height {
			max-height: 500px;
		}'
	]);
});