Flex is somewhat supported in IE, but there are problems when it is mixed with other things. For example, there is no problem when aligning alone, but when mixed with UIKit, Flex behaves strangely in IE. So if you have to consider IE even a little, it is true that you are hesitant to use Flex, let alone Grid. However, since all the basic properties of Flex are supported in IE, you do not have to worry too much about using it.