No, bearded dragons cannot safely eat spinach.
The reason being is that spinach is calcium-binding which means it prevents the lizard from metabolizing calcium.
So if a bearded dragon was to accidentally eat a few leaves they won’t die but it is best for them to avoid this vegetable all together as it is bad for them.
Another thing is that the calcium to phosphorus ratio is over 2:1 which is bad for beardies. Also spinach is high in acidic content which is bad for bearded dragons.