WP User Manager - Fix account/profile sub-page templates in WP 6.0+

wpum_fix_account_profile_page_template.php

<?php

add_filter( 'template_include', function ( $template ) {
	global $wp;

	if ( ! isset( $wp->query_vars ) ) {
		return $template;
	}

	if ( ! isset( $wp->query_vars['page_id'] ) ) {
		return $template;
	}

	if ( $wp->query_vars['page_id'] === wpum_get_core_page_id( 'account' ) || $wp->query_vars['page_id'] === wpum_get_core_page_id( 'profile' ) ) {
		$new_template_slug = get_page_template_slug( $wp->query_vars['page_id'] );
		if ( $new_template_slug && basename( $template ) !== $new_template_slug ) {
			$template = dirname( $template ) . '/' . $new_template_slug;
		}
	}

	return $template;
}, 100 );

Save this file to your /wp-content/mu-plugins/ directory (you might need to create the mu-plugins directory).