CPT EVENT - listing by month and filtering by category and month - form select option

I am creating custom post type eventlist filter form. There is two options: category and months. Following this advice List events by month I got display event categories by month. Meaning...

January

• Event post 1
• Event post 2

February

• Event post 1
• Event post 2

etc.

Category choosing works smoothly. Problem comes up when user choose month. By default events are listed by month. How can I reorder events using form options? Is it possible solve using meta_query compare or do I need some other solution?

form method=get action=?php the_permalink();? name=tapahtumalista
select class=form-select name=kat

?php 
$terms = get_terms( array(
    'taxonomy'      = 'kategori_tapahtumat',
));


// SELECT OPTION CATEGORY
?

    option value=Valitse kategoria/option
    ?php 
    
    foreach ($terms as $term) { ?
        option value=?php echo $term-slug; ? ?php if(isset($_GET['kat'])  $_GET['kat'] == $term-slug) { echo 'selected=selected'; }?
        ?php echo $term-name; ?/option
    ?php } ?
/select

?php  // SELECT OPTION MONTH ?
select class=form-select name=kk
    option value=Valitse kuukausi/option
    ?php 
    for ($i = 1; $i = 12; $i++){
    $month_name = date_i18n('F', mktime(0, 0, 0, $i, 1, 2011)); 
    $month = !empty( $_GET['kk'] ) ? $_GET['kk'] : 0;
    $selected = $month_name == $month;
    ?
    option value=?php echo $month_name; ? 
    ?php if(isset($_GET['kk'])  !empty($_GET['kk']) == $selected) { echo 'selected=selected'; }?
    ?php $selected ? 
        ?php echo $month_name; ?
    /option
    
    ?php }?
/select
input type=submit name= value=Valitse

// Selected category from form option 
if($_GET['kat']  !empty($_GET['kat'])) {
    $selected_cat = $_GET['kat'];
}

//Selected month from form option
if($_GET['kk']  !empty($_GET['kk'])) {
    $selected_month = $_GET['kk'];  
}


$today = date('Ymd');
$m = get_the_time('m');

$args =  [
    'post_type'         = 'tapahtumat',
    'post_status'       = 'publish',
    'posts_per_page'    = - 1,
    'meta_key'          = 'aloituspaiva', //event start date
    'meta_value'        = $today,
    'orderby'           = 'meta_value',
    'value'             = $today,
    'meta_compare'      = '=',
    'type'              = 'DATE',
    'order'             = 'ASC',
    'tax_query'         = [
        [
            'taxonomy'  = 'kategori_tapahtumat',
            'field'     = 'slug',
            'terms'     = $selected_cat, //category get from form 
        ]
    ],
    'meta_query'        = [
        'relation'      = 'OR',
        [
            
            'month'     = $m,
            'value'     = $selected_month, // get from form possible?
            'compare'   = '=',
        ]

    ]
];
$query = new WP_Query($args);

// List events by month (default view) - using dboris solution

$all_events = [];

if($query-have_posts()) :
    while ($query-have_posts() ) : $query-the_post();
        $date = strtotime(get_post_meta( get_the_ID(), 'aloituspaiva', true ) );
        $month_year = date( F, $date );
        $all_events[ $month_year ][] = $query-post;    
    endwhile;
    // Sorting events by month

    foreach ( $all_events as $month_year = $events) : ?
        ?php echo 'brbrstrong' . $month_year . '/strongbr';  ?

        ?php foreach ( $events as $event ) : ?
            ?php echo $event-post_title . 'br';?
        ?php endforeach;?
    ?php endforeach;
else :
    echo ('No results.');
endif;

wp_reset_postdata();