I frequently use my Galaxy Tab S8 in landscape orientation. As far as I can find, even with a new update, the S Note app does not have an option to reorient pages into landscape orientation. You can certainly rotate the tablet, and all of the tools and the interface rotates, but the page itself that you are working on stays in portrait. I wouldn't want it changing randomly, but since you can select different sizes of "paper", it seems like there should be an option to select a landscape orientation.
There are some solutions online suggesting importing a PDF page that is blank which is in the orientation you want, but you can't switch PDFs to dark mode. So it kind of kills that cool feature that S Note has which allows you to work with a black background. (But then still be able to print with a white background if you need to print your notes)
(I tried finding a spot to submit feedback directly to Samsung from within an app or within the members app as a lot of places have suggested, but I cannot find an option so I'm posting here.)
