Thanks for the hint!
I really need to remember the github repository for the yunohost apps.
I edited the /etc/php/8.0/fpm/pool.d/lychee.conf file removing the comment at the lines
php_admin_value[upload_max_filesize] = 50M
php_admin_value[post_max_size] = 50M
restarted the php8.0-fpm service and now it works!