An ultrawide lens (anything below 24 mm in 35 mm equivalent format) can provide a sweeping view of an open landscape, but I also find it important for crowded forest and tree covered environments.
The widest rectilinear lens I own is an 11 mm lens by Irix and it is an excellent lens, but these pictures are made with other lenses. They are landscapes I made while testing an ultra wide 11 mm lens by Venus Optics on my Z7 alongside a 12 mm Samyang fisheye lens. I no longer own either lens but the photos I made that afternoon are good representatives of what can be done with these optics.
One thing I sometimes dislike about ultra wide rectilinear lenses is that elements in the corners of the image can look too stretched, like sucked into the frame. Because of this, I sometimes actually prefer using a fisheye lens: when used carefully, one can can hide the strong deformation we associate with their extreme projection. By keeping the horizon near the center of the frame, it remains straight on a fisheye lens image. In other cases, the image can be reprojected (defished as some people call it) to avoid the curved corners.
You can be the judge now and decide if this approach works as I really wanted to include nearby elements from a restricted point of view: I was literally shooting from a barbed-wire fence in all the photos I show here.
Have you tried using fisheye lenses for landscape photos?