The Canon RF 14-35mm f/4L IS USM lens is a high-quality zoom lens that is perfect for capturing wide-angle and ultra-wide-angle photos. The lens has a maximum aperture of f/4 and is part of the Canon "L" series, which is known for its excellent image quality.
I bit the bullet and went for the F/4 over the F/2.8 because (a) of the extra millimeter of wide angle over the 15-35, and (b) it was just a little more than half the price. It turned out to be a great idea! The lens is very lightweight, and delivers professional quality results.