lifterlms-catalog-compat-add-wrappers.php

<?php // don't copy this line to your functions.php file

add_action( 'lifterlms_before_main_content', 'my_content_wrapper_open', 10 );
add_action( 'lifterlms_after_main_content', 'my_content_wrapper_close', 10 );

function my_content_wrapper_open() {
	echo '<section class="my-wrapper-class" id="main">';
}

function my_content_wrapper_close() {
	echo '</section>';
}

lifterlms-catalog-compat-remove-defaults.php

<?php // don't copy this line to your functions.php file
remove_action( 'lifterlms_before_main_content', 'lifterlms_output_content_wrapper', 10 );
remove_action( 'lifterlms_after_main_content', 'lifterlms_output_content_wrapper_end', 10 );