Is it same if I say just "must not buy 5g"? Why does he put "any" here?
"Any" is a word that is commonly used to add emphasis to something. When the speaker says "must not buy any 5G equipment from Huawei," he is stressing that not a certain amount, or a single piece of 5G equipment, can be purchased from the company. It is a little more forceful than simply saying "must not buy 5G equipment." Ex: I am on a diet, so I can't eat any snacks. Ex: Is there any cake left?