how to change the Mac address without rooting your phone I do have a Samsung Galaxy J5 2016, and I am trying to change its MAC address without rooting it.

I've done a lot of internet search, and I've come across many useful guides and advice, such as 
https://www.quora.com/How-can-I-change-my-Android-non-rooted-Mac-address.

Anyway, Terminal Emulator doesn't allow the operation indicated in the guide (ip link set...etc etc.): it outputs permission denied.

More search gives as a result that you can't do this command without logging as superuser and, in turn, that you can't do that if you aren't on a rooted device.

So I'm starting feeling as I'm chasing my tail...

Can anybody please help?
Simply, you can't. Because of how the permissions work in Linux, what android is built on, you are required to use a root account to make those changes. The root account being su, which is only accessible when you have a rooted device. To my knowledge there is no way around that, even using alternate commands that might exist.