Maybe-kinda-late-initializing classes in WordPress?

hookable-trait.php

<?php

trait Hookable {
	public static function get_instance() {
		static $instance = null;

		if ( is_null( $instance ) ) {
			$instance = new static();
		}

		return $instance;
	}

	public static function add_filter( $hook, $priority = 10, $accepted_args = 1 ) {
		// You could transform $method to whatever suits your style
		// Right now it could end up like "the_content_filter", but if you prefer
		// camelCase for method names, you could convert $hook to camelCase and
		// add Filter to it so that $method would end up like "theContentFilter"
		$method = $hook . '_filter';

		// method_exists seems to work regardless of a method's visibility or static/regular type
		if ( ! method_exists( static::class, $method ) ) {
			// maybe show/log an error message here that this would not work
			// due to absence of $method on the current class
			return;
		}

		add_filter( $hook, function() use( $method ) {
			$instance = static::get_instance();

			return call_user_func_array( [ $instance, $method ], func_get_args() );
		}, $priority, $accepted_args );
	}

	public static function add_action( $hook, $priority = 10, $accepted_args = 1 ) {
		// You could transform $method to whatever suits your style
		// Right now it could end up like "the_content_action", but if you prefer
		// camelCase for method names, you could convert $hook to camelCase and
		// add Filter to it so that $method would end up like "theContentAction"
		$method = $hook . '_action';

		// method_exists seems to work regardless of a method's visibility or static/regular type
		if ( ! method_exists( static::class, $method ) ) {
			// maybe show/log an error message here that this would not work
			// due to absence of $method on the current class
			return;
		}

		add_action( $hook, function() use( $method ) {
			$instance = static::get_instance();

			call_user_func_array( [ $instance, $method ], func_get_args() );
		}, $priority, $accepted_args );
	}
}

myplugin.php

<?php

/* Your plugin headers here, if this is a plugin */

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly.
}

require_once __DIR__ . '/hookable-trait.php';
require_once __DIR__ . '/MySampleClass.php';

// Register the hooks for the class without instantiating it by using a static method
MySampleClass::register_hooks();

MySampleClass.php

<?php

class MySampleClass {
	use Hookable;

	public static function register_hooks() {
		static::add_action( 'wp_footer' );

		static::add_filter( 'the_content', 100 );
		static::add_filter( 'admin_title', 100, 2 );
	}

	public function wp_footer_action() {
		echo '<h1>This is wp_footer_action()!</h1>';
	}

	public function the_content_filter( $content ) {
		$content .= '<h3>I added this from a filter!</h3>';

		return $content;
	}

	public function admin_title_filter( $admin_title, $title ) {
		return $admin_title . ' <==== Test, also received $title: ' . $title;
	}
}