Canon´s 11-24mm lens is top-heavy, but does not provide for a tripod support. This is particularly worrisome when mounted on a small mirrorless camera. Some adapters, such as the Metabones, have a tripod mount, but it is rather flimsy and hardly accessible when a battery grip has been added to the camera. The lens has some space between zoom and distance rings, but there is a protruding distance scale and a protruding AF switch. With some ingenuity, it would still seem possible to mount a ring support there, preferably even a revolving one, to allow easy vertical shots. Has anyone made some progress in this direction?
If your mirrorless camera has a smaller than full-frame sensor (36 mm × 24mm), then stop. The Canon EF 11–24mm f/4.0 L USM lens is designed for full-frame cameras, and is expensive ($3000 USD) and wasteful for crop sensor cameras.
Instead you should look at wider focal length, bigger aperture, yet cheaper lenses such as the Canon EF-S 10–22mm f/3.5–4.5 USM lens ($600) or EF-S 10-18mm f/4.5–5.6 IS STM lens ($300). There are other non-Canon lenses with even wider focal lengths that are suitable for crop sensors.
Otherwise if your mirrorless camera does have a full-frame sensor (basically only Sony ones right now) then the advice in Dan Wolfgang's comment is applicable. I don't expect the weight of the lens would cause any mechanical problems.
I have found very few somewhat useful solutions in the internet. The solution I had envisaged I obtained today from Zoerk in Munich (try www.zoerk.de, the us website may not be up to date). This solution consists of a protecting ring mounted on the lens and an aluminium chain-ring with a tripod support. It can also be used for vertical camera orientation without any loss of stability. (Additional stability can of course be obtained by adding a monopod support for camera or adapter, which might be useful for multi-minute exposures using high-density gray filters). Also: the same chain (but with another protecting ring on the lens) can be used for the Canon TS-E sense 17mm and 24mm II, thus enabling easy panoramas by shifting the camera.