Using meta_query with non-meta_query criteria in a WP_Query using OR instead of AND

You’re better off running two queries, then merging the results.

$first = get_posts( [
    'fields' => 'ids',
    's' => $s,
    // ...
] );

$second = get_posts( [
   'fields' => 'ids',
   'meta_query' => ...
] );

$ids = array_values( array_unique( array_merge( $first, $second ) ) );

$query_args = [
    'post__in' => $ids,
    // ...
];

If your posts and postmeta tables are large and you’re concerned with performance, then you should be looking to run your searches on a proper index like Sphinx, Elasticsearch, etc., or build your own indexed column inside MySQL on wp_posts.