You can order topics within a category by creation date with
?order=created but you can’t do that with tags.
The only workaround is to use the search feature but this feature has limitations. For instance it doesn’t show more than 175 results (e.g. Search results for '#pr-welcome order:latest_topic' - Discourse Meta)
Also it doesn’t work with several plugins.
A real solution like
order=created would solve that.