I ended up adding this code at Line 306:
$blogname = esc_html( get_option('blogname') );
$blogname = qtranxf_use($recipient->lang, $blogname);
$blogdescription = esc_html( get_option('blogdescription') );
$blogdescription = qtranxf_use($recipient->lang, $blogdescription);
It works for the blogname and blogdescription part, but I was not able to have the date translated to the correct recipients language. I changed the way WordPress was displaying the date for now… to show it without the month name.
I also changed lines 537 to 540 to this:
$blogname = esc_html( get_option('blogname') );
$blogname = qtranxf_use($recipient->lang, $blogname);
$content = str_replace("[SITE-LINK]", "<a href='". qtranxf_convertURL($trackable_home_url) /*esc_url ( alo_em_translate_home_url ( $recipient->lang ) )*/ ."'>". $blogname ."</a>", $content);
because the link and the link label were not translated.
I’m sure this is not the way it should be but it is working for me for now, until there’s a better solution I’ll use this.