So recently I just wanted to see the posts of a FB group ordered by the date of posting descending. I know for sure that there used to be such a feature and I'm sad to see that it's no more, because it's more important for such companies to remove useful features and add useless ones (like who tf wanted to see their friends' stories in their feeds and make them seen when scrolled over when there's already such a section on the top of the page and you can deliberately decide whether to click on them or not).
Fortunately for me, last year I saved a few links as bookmarks of groups where I had this ordering selected. Now I checked and it still works.
In order to change the ordering all you have to do is append the ?sorting_setting=CHRONOLOGICAL to the URL
to get rid of the random magic ordering.