How to filter elements by meta key from dropdown menu

Question

I'm building a site to show Artists with a list of their releases.

Here's Madonna's Page as an example.

Each page has a list of filter options in a dropdown menu. I'd like to auto-populate those dropdowns with each unique item from a meta-key. Examples are "country of release" and "fortmat". So in the dropdown menu for "format", I'd like it to autopopulate with each type of format she has a release for. Then when you click on one, I'd like to filter the results to only show that format.

Same with year, country, etc. I have the list auto-populating and showing "Releases" but I don't know how to apply a filter to that one.

I can't get the rest to show up. Here's the code for the working dropdown "Releases"

<select>
            <option selected="selected">Label</option>
            <?php 
                    $format_args = array(
                        'numberposts' => -1,
                        'meta_query' => array(
                            array(
                                'key' => 'wpcf-format',
                            
                    )
                )
                );
                
                $format_posts = types_child_posts('release', $format_args);
                
                

                // sort alphabetically by firstname and lastname
                usort($format_posts, 'compare_fullname');

                
                    $url = esc_url( home_url() );
                
                ?>
                <?php foreach ($format_posts as $format_post)  {      
                    echo "<option value='Releases'>$format_post</option>";
                }
            ?>
        </select>
        <select>
            <option selected="selected">Picture Disc</option>
                <option value="All Releases">All Releases</option>
                <option value="Picture Disc Only">Picture Disc Only</option>
                <option value="No Picture Discs">No Picture Discs</option>
        </select>
        <select>
            <option selected="selected">Bootleg</option>
                <option value="All Releases">All Releases</option>
                <option value="Bootleg Only">Bootleg Only</option>
                <option value="No Bootlegs">No Bootleg</option>
                
            
        </select>

Here's the code for one I want to work, but isn't populating.

<select>
            <option selected="selected">Year</option>
            <?php 
                    $year_args = array(
                        'numberposts' => -1,
                        'meta_query' => array(
                            array(
                                'key' => 'wpcf-year-release',
                            
                    )
                )
                );
                
                $year_posts = types_child_posts('release', $year_args);
                
                    $url = esc_url( home_url() );
                
                ?>
                <?php foreach ($year_posts as $child_post)  {      
                    echo "<option value='year'>$child_post->wpcf-year-release</option>";
                }
            ?>
        </select>

How do I apply a filter to the releases shown so that only releases matching the selected meta-key from the dropdown menu are shown?

Thanks!