To add to @Aurix’s comment, there is a way to search for a user’s posts chronologically. This method has a drawback of only showing the posts that have the author’s username in them though.
It’s also technically possible to emulate the function you want. It’s nowhere near perfect, but it’s a thing. Go into full page search, open Advanced options and choose “I’ve not read”. Then sort by Latest post. This search will still show the topics where you haven’t read the latest comment, but it will show them in chronological order, which is better than nothing.
