You can simply add more attachments type using the “fluent_support/mime_groups” filter. To add more attachments type use “add_filter” hook.

// Add mime type to existing mimes
add_filter("fluent_support/mime_groups", function($mimeTypes){
    $mimeTypes['images']['mimes'][] = 'image/avif';
    return $mimeTypes;
});

// Add new mime group
add_filter("fluent_support/mime_groups", function($mimeTypes){
    $mimeTypes['html'] = [
       'title' => __('HTML', 'fluent-support'),
       'mimes' => [
           'text/html'
       ],
    ];
    return $mimeTypes;
});