Are Uyuni salt flat tours safe?

Yes, Uyuni tours are generally safe when you go with reputable, highly rated tour operators. But risks are there, like altitude sickness, extreme cold, or reckless driving from cheaper operators, which happens more than people expect.

For safer travel, read recent reviews carefully before booking and do not chase the absolute cheapest price. Confirm that they supply oxygen tanks in their vehicles, that the 4x4s are well maintained, and that the drivers do not drink during working hours, since this was a recurring issue. The local tourism board has pushed pretty hard on it in the last few years, so you should still verify it, though.