Meta_query 'compare' => 'LIKE' not working?

If the query string contains, as you say:
listing_i_have=own%20studio

It’s not working because $rt_field_id_i_have[0] is equal to the first character in the string (it’s not an array), it’s a string. The 0 index position is the letter o, which matches A LOT of things.

You can add the proper meta query like so.

<?php
function rt_tax_archive($query) {
    if (is_admin()) {
        return;
    } elseif ( ! $query->is_main_query() ) {
        return;
    } elseif ( ! isset( $_GET['ls'] ) ) {
       return;
    } elseif ( empty( $_GET['listing_i_have'] ) ) {
       return;
    } elseif ( ! is_string( $_GET['listing_i_have'] ) ) {
       return;
    }
    $rt_field_id_i_have = wp_unslash( $_GET['listing_i_have'] );
    $rt_field_id_i_have = sanitize_text_field( $rt_field_id_i_have );

    $query->set('meta_query', array(
        'key'    => 'app_i_have',
        'value'  => $rt_field_id_i_have,
        'compare'=> 'LIKE',
    ));
}
add_action( 'pre_get_posts', 'rt_tax_archive' );

It’s worth noting that when using LIKE, WordPress automatically wraps the value inside %[value]%, so you don’t need to include the LIKE wildcards yourself. You weren’t doing so, just thought I’d mention that for posterity.

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