Blog Excerpt

ah sorry – now i see that you have masonry in use.
I prefer on this to limit the excerpt on word basis.
f.e. this on child-theme functions.php:

function custom_excerpt_amount(){
?>
<script>
(function($){
// trim excerpt by words
    function trimByWord(sentence,wordcount = 10) {
        var result = sentence;
        var resultArray = result.split(" ");
        if(resultArray.length > wordcount){
        resultArray = resultArray.slice(0, wordcount);
        result = resultArray.join(" ") + "...";
        }
        return result;
    }
    $(document).ready(function(){
        // here is the place to choose the right selector
        $('.av-masonry-entry .av-masonry-entry-content').each(function() {
             $(this).text(function(index, currentText) {
                return trimByWord(currentText);
             });
        });
    });
})(jQuery);
</script>
<?php
}
add_action('wp_head', 'custom_excerpt_amount');

but this jquery solution does not work nice on “Load more” Masonries.

but the filter you decided to use is ok. – maybe it is just a matter of the accepted args value – leave without that:

function avia_change_masonry_excerpt_length($length){
	$length = 200;
	return $length;
}
add_filter('avf_masonry_excerpt_length','avia_change_masonry_excerpt_length', 10 );

yes – and i comment in that code above ( jquery code ) that i do not see your page you are referring to. This line in the code :

$('.av-masonry-entry .av-masonry-entry-content').each(function() {

had to be adjusted to the selectors that will work on your page – i can not give better advice if i do not see the concrete page it concerns
and since I am a participant like you I do not see the link if it is in the private content area.

so – now i could find your page – your nick is informative enough on that ;)

function custom_excerpt_amount(){
?>
<script>
(function($){
// trim excerpt by words
    function trimByWord(sentence,wordcount = 10) {
        var result = sentence;
        var resultArray = result.split(" ");
        if(resultArray.length > wordcount){
        resultArray = resultArray.slice(0, wordcount);
        result = resultArray.join(" ") + "...";
        }
        return result;
    }
    $(document).ready(function(){
        // here is the place to choose the right selector
        $('.avia-content-slider .slide-entry-excerpt').each(function() {
             $(this).text(function(index, currentText) {
                return trimByWord(currentText);
             });
        });
    });
})(jQuery);
</script>
<?php
}
add_action('wp_head', 'custom_excerpt_amount');

and with the css code from beginning – you see that now the slide-meta like the date is then in one line at the bottom:

#top.blog .avia-content-slider .slide-entry-wrap {
  display: flex;
  flex-flow: row wrap;
}

#top.blog .slide-content {
  padding-bottom: 60px;
}

#top.blog .entry-footer {
  display: ;
  position: absolute;
  bottom: 0;
  top: auto;
}