Anyone know how to fix this

The plugin developer dosen`t answer anymore and maybe someone from here know how to fix this
[16-Aug-2024 17:14:25 UTC] PHP Deprecated: strtolower(): Passing null to parameter #1 ($string) of type string is deprecated in /home/x/x/x.com/public_html/wp-content/plugins/WP AMP/vendor/simple_html_dom.php on line 759

This is the line 759

                $key = strtolower( $key );

[16-Aug-2024 17:14:27 UTC] PHP Deprecated: Creation of dynamic property AMPHTML_Sanitize::$element_default_height is deprecated in /home/x/x/x.com/public_html/wp-content/plugins/WP AMP/includes/class-amphtml-sanitize.php on line 42
[16-Aug-2024 17:14:27 UTC] PHP Deprecated: Creation of dynamic property AMPHTML_Sanitize::$element_default_width is deprecated in /home/x/x/x.com/public_html/wp-content/plugins/WP AMP/includes/class-amphtml-sanitize.php on line 43

        $this->element_default_height = $this->template->get_option( 'element_height' );
        $this->element_default_width  = $this->template->get_option( 'content_width' );

Downgrade to php 8.1