500 errors on PHP 7.4

Hopefully this is helpful. My site is breaking because your plugin is not compatible with versions of PHP lower than PHP 8.

This is because of the following code:

In includes/rest-api.php:

public function create_feedback( WP_REST_Request $request ) {
		$content_type = $request->get_header( 'Content-Type' );

		if ( ! str_starts_with( $content_type, 'multipart/form-data' ) ) {
			return new WP_Error( 'wpcf7_unsupported_media_type',
				__( "The request payload format is not supported.", 'contact-form-7' ),
				array( 'status' => 415 )
			);
		}

To make this work with PHP 7.4 I had to update as follows:

public function create_feedback( WP_REST_Request $request ) {
		$content_type = $request->get_header( 'Content-Type' );

		//if ( ! str_starts_with( $content_type, 'multipart/form-data' ) ) {
		if (!substr($content_type, 0, strlen('multipart/form-data')) === 'multipart/form-data') {
			return new WP_Error( 'wpcf7_unsupported_media_type',
				__( "The request payload format is not supported.", 'contact-form-7' ),
				array( 'status' => 415 )
			);
		}

The current version of WordPress supports PHP 7.4 so you may want to update your plugin accordingly as I expect there will be lots of people experiencing this issue.