Landscape is not available.
No idea why, this has been requested for about two years, By both Samsung and Apple users , and there’s never been an answer.
As you mentioned, it would be very helpful for wall-mounted tablets. It’s also important for those of us in wheelchairs with tablet mounts.
There’s no harm in asking again, but it doesn’t appear to be a priority. The app has gone through at least two major redesigns during this period and landscape has never been added. 