Great. I tend to have to chop my grape leaves up a bit and mix with other foods only because they are so flat they are a little hard for my tortoise to pick up and eat.
Any cactus is fine; they are all full of fiber and calcium. Most folks here use spineless opuntia, because it’s widely available and has no big spikes. Our wild desert tortoises eat cactus with spikes all the time in their natural habitat but big spines make most owners nervous. You can burn off the spines or cut them off. Little pricklies are fine but some people cut or scrub them off as well. If you can get access to a pad of spineless opuntia it’s pretty easy to grow.
This is what the spineless one looks like, I feed it to my Russian without any prep:
UPDATE: I switched up my search methods, and, at long last, I finally found the Fountain of Youth. A store filled to the brim with endive, corn salad, dark lettuce of all forms, wild rocket, and countless other greens that any tort yearning for variety would kill for. Looks like not overlooking the obvious searching spots paid off, didn't it...
So now my staple is this mixture of 25% rocket, 20% parsley, 25% dark lettuce, and 30% whatever is available (corn salad, dandelions, radish greens, etc.). Sounds good?
Feed less radish and rocket and more chicories and you are doing well.
I would personally go fiftyish-sixtyish percent in the chicory family: endive/dandelion/frisee/radicchio/escarole. These are lettuces have less sugar and more fiber, which is what we want. Include some of the floppier dark lettuces in there but not too many.
Thirtyish percent rocket/turnip and radish greens/bok choy. These is another plant family (brassicas) that is good for tortoises, as they are high in calcium, they just shouldn’t be the primary foods. Feel free to mix in the other interesting things you find on occasion, like corn salad.
You don’t have to feed all of these at the same time, of course!
You’ll still be missing fiber with these foods and will need to include the cactus, grape leaves, or prepared supplement.