My idea would be adding a knob (perhaps named ‘type’ or ‘level’) at the left side of ‘location’ of the frontpage to toggle between posts/comments.

I hope I understand your concern correctly. I think being near sorting is okay because actually the ‘feeds of comments’ also needs sorting algorithms. You may check lemmy-ui and Alexandrite sites as references. Besides, the options of sorting algos may be the same as ‘feeds of posts’ except ‘comments’.