The workhorse lens of choice for a huge range of photographers is the 24-70mm f/2.8, and while it is an extremely useful optic, there might be better choices for certain genres and photographers. For landscape work, an interesting alternative is a 24-105mm f/4 lens, and this great video discusses why it might be the essential lens for such imagery.
Coming to you from Photo Tom, this awesome video discusses the virtues of a 24-105mm f/4 lens for landscape photography. While a 24-70mm f/2.8 lens is quite useful, for landscape work, such a wide aperture is not generally necessary, and in addition to offering extra reach on the long end, a 24-105mm lens tends to be lighter and considerably cheaper, making it a compelling alternative. I owned the original Canon EF 24-105mm f/4L lens for a long time, and according to my Lightroom statistics, it was my most used lens by far for several years. It was such a versatile and useful combination that I took it almost everywhere with me. Check out the video above for the full rundown.
And if you really want to dive into landscape photography, check out "Photographing The World 1: Landscape Photography and Post-Processing with Elia Locardi."
The 24-105mm f/4 is very old but very good!! I used to use on my Canon also. Landscape photography is a very tangled term. You can go wide with a close subject with wide background or long for close up of a far off subject but still look like a wide landscape. Even a stream in the woods is a landscape, but how much do you want of it is the problem when out in that far off place. First fast glass is really not needed, as with the 24-105 f/4, for if you test a lens for sharpness 2 stops above wide open is generally it, so f/4 is great at f/8 but f/11 will be good also. The other problem is your someplace you have never been or it is just another day with different weather and light. A landscaper is like Columbus going to a new world and like eating a box of chocolates never knowing what you will get for it is the photographers' eye and what is seen both neer and far that needs to be prepared for. When I went Sony some years back I used my Canon lenses with an adapter for a few years till some Sony's came out like the 10-21, 16mm in APS-C mode but an old Sony APS-C 10-18, 15-27 BUT in full frame 12-18mm (18mm if the light shield is removed) so playing you get 12-27 with one very light lens that has threads for filters and IS so you can hold and shoot. But wide is not for getting it all in for it is about subjects one sees both far and near and the 24-105 was great.
If you are Sony my recommendation is the 1224mm f/4 or f/2.8 and the 24-240 (on sensor 360 in APS-C) and can be carried even with two bodys in a teardrop bag with two pockets on both sides and extra small pockets for stuff. But if you can get the 200-600mm (900 APS-C), yes very big and you need a backpack but it can also be carried on a heavy duty binocular harness and ready to put a body on or with one on all under a light or heavy jacket (unseen) but put a camo Lenscoat on to cover the white (wildlife spook with white or black (think is a gun). As a hobbyist I like long walks but without a backpack unless I am camping somewhere and I have food and clothing in one. Be ready for it with the mm or mm's you need.
I also find the Canon 24-105 to be extremely useful and versatile and most my landscapes are shot with it. I find the reach of 105 vs 70 to be a huge factor in the versatility. If I do need more reach I mount the 100-400MM MII and go for it as it also is relatively light and compact for what it is. The near macro also makes it the must bring on a walk in nature lens as no one else comes close to the near macro and versatility of the 100-400mm MII. But the 24-105mm is always with me and generally on the camera especially when looking at landscapes.
24-105 is a winner, excellent optics, good zoom range, fast enough for most situations and a reasonable price. This lens and a 50mm is a complete kit for most folks