Dark green leafy veg such as kale and broccoli have lots of available calcium.
Unfortunately spinach not so much.
Whole Soya beans do too.
Much of Asia can't digest dairy at all.
It's something we in the West have evolved our gut biome to do.
They get their calcium from above sources.
And don't forget fish like sardines, whitebait, etc where you crunch up the bones. Lots of calcium in there.
Nettles - such as are coming through green and lush right now, are also a very good source of calcium.
They make a really nice soup with a bit of sautéed onion leek, potato, carrot, etc, plus veg stock, then whizzed up with one if those hand blender wand thingies.
Even nicer with grated cheese on top.
But you can get this stuff called engevita, from wholefood shops which makes a good soup topping.
Looks like fish food, but is actually yeast flakes.. Tastes quite nice and cheesey, and has all the B vitamins that some folks on vegan / restricted diets struggle to get.