Receiving calls from PSTN, "s" extension or dialed number?

Hello,

If I understood correctly, to receive calls from the PSTN, I must create an extension either named “s”, or the dialed number.

exten => s, … or exten => 045678432, …

What would be the difference between these two ways of doing it?
PS: I get calls from the PSTN through a Digium card FXO

Depends whether or not you have direct in dialing. In the latter case, it is not necessarily the full number, it is whatever the PSTN operator forwards.

However, I don’t believe that Asterisk supports DID on analogue lines.

The easiest way is to look at the logs and see what number it fails to find in the incoming PSTN call context.

It doesn’t.