I don't see why those shouldn't work. Personally, I find that method to be "the long way." There is an Add item in the context menu for the RSS Feed entry in the Outlook Folder Tree and it pretty much walks you right through adding the feed URL that you have.
This is one of those, "It's not rocket science," sort of things. More of a "fill in the blank with the correct RSS Feed URL" and hit OK. (There may be a couple of more steps, but I don't want to fully configure an RSS Feed I don't want.)
Brian - Windows 10, 64-Bit, Version 21H1, Build 19043
It is better to be hated for what you are than to be loved for what you are not.
~ André Gide