Surely this is "do you hear me" rather than "can you hear me"?
Both are valid and equally accepted.
why not "peux-tu m'entendre"?
It is possible, but be aware that it is not the most common way of saying this. In French, the verb "pouvoir" is not used in such situations: "m'entendez-vous / m'entends-tu ?"
'Salut, est-ce que tu m'entends?' was not accepted