POTS to SIP with cheap hardware

Hi everyone, i am new to the asterisk world, so feel free to tell me if i am posting in the wrong place.

My question is simple: being totally ignorant on asterisk and PBX systems, i was wondering if it was possible to basically use my wifi-enabled smartphone as a POTS (landline) cordless phone when i’m at home, connected to my wlan.
Now i got a 56k USB voice modem, and i was thinking about hooking it up to a pc, or even better a raspberry pi, and use that as a gateway to route my voice traffic over my home LAN.
I won’t consider a VOIP line, because here in Italy those aren’t so diffused, and because I already have a good voice plan on the land line, so i would like to use it.

I talked to a (nerdy) friend who suggested me to setup an asterisk server, but now i am just confused on what to do, and how to do that.

I’ll appreciate any kind of help and suggestions, even if my idea is not feasible…

Asterisk doesn’t support normal voice modems.

Thank you!

I’ll start considering on getting some serious hardware…

Earlier versions of Asterisk supported a very specific type winmodem, X100P (sold as a cheap line card). I’m sure that code has not been maintained for some time and it may even no longer work.