there is no KNOX on my phone . is my data after formatting protected?

Yes it is. Internal storage encryption has been a standard feature since Android 6. Knox was originally intended for enterprises, to keep their Samsung Galaxy devices secure and locked-down,.

Presumably Samsung didn't intend the M30s for company use, why it doesn't have Knox.

 

It's an interesting question. Regardless of KNOX encryption has been standard on Android devices since about 5.0. But FBE came in with Android 7, while Full Disk Encrytion was available from 5 to 9. So while I'd expect your device to be encrypted (because storage has been encrypted by default for some time) I can't be sure just from the Android version which type of encryption would have been used. My answer in your other thread was assuming the more modern system (FBE), but I realise I can't be certain.

However, I suspect my answer still stands: the older Fill-Disk Encryption your password is used in the hashing of the master key, but it's not the full encryption key itself (the device creates a random key on first boot, and I'm pretty certain that is erased by the reset and a new one created). So I don't think you can easily recover your data using it.

 

The data is definitely encrypted(to AES256), as it is on all Android device since Android 6. And is NOT recoverable after a factory reset, as the encryption key is deleted during a factory reset.

Samsung Knox can work with the stock Android storage encryption. Knox is Samsung's feature to make it easier for companies to administer and control their fleet devices, that's it. For example, companies can enforce passwords to unlock their Samsung phones, can provide a remote kill switch, and prevents employees from installing their own whatever apps on company owned devices. That's basically what Knox does.

FYI about Samsung Knox:
https://www.samsungknox.com/en
"A complete suite of enterprise mobility solutions designed to keep your work phones, tablets, and wearables under IT control. So you can focus on your business."


Apparently Samsung didn't intend the M30s for company fleet use, unlike say their Galaxy S and Note series, that's why it doesn't have Knox.

 

Phones initially released with android 4.4 and earlier can revert to an unencrypted state after a reset (though the data that were erased by the reset were encrypted, it's data added after the reset that may not be). A phone initially released with 9 will not.

KNOX is irrelevant to this:android has encryption independent of Samsung's KNOX add-on.