OK, in the URL we guess if desc means descending, what might ascending be... we guess wrong, but do trigger this message.

A warning has occurred while searching: Sort order of last_edit_acenc is unrecognized, default sorting will be applied. Valid sort orders are: relevance, just_match, none, incoming_links_asc, incoming_links_desc, last_edit_asc, last_edit_desc, create_timestamp_asc, create_timestamp_desc, random

OK, in the URL I used sort=last_edit_asc and what do you know, it worked.
Therefore the problem is just with the menu not mentioning it though it already works!

And this stimulates the menu to grow...