Cannot navigate magazines with keyboard or mouse inside News app on Mac OS

(This was originally raised by user chuckst Apr 2020. The answer (a link to Mac keyboard commands) was not helpful and did NOT show how to navigate a magazine article with keyboard or mouse. Not being able to scroll thru/page up/down with something intuitive like arrow keys or PgUp/Dn keys is a real UX flaw.)

How do I navigate within a magazine on my desktop using Apple News+ ?

I am a subscriber to Apple News+ and wanted to read a magazine which I found but when I opened it the window shows a huge graphic of the cover on the left and thumbnails of inside pages on the right. So far so good. When I mouse click on the article I'd like to read that page now fills the screen but I can't seem to use the keyboard or mouse to advance the next page. All I've been able to do is toggle back and forth between the first window and an individual page. The keyboard advance arrows or scrolling with the mouse do not work.

You CAN navigate . . .but only by selecting the app's View menu and clicking on Next Page and Previous Page. This is quite inconvenient.

For anyone else experiencing this problem, one alternative is using a trackpad (I got myself a Magic trackpad) and doing a two-finger swipe left or right while inside a magazine story. Still, not having a mouse or keyboard option to navigate inside a magazine seems like a real gap.