Dialup could be had for very cheap last time I had if (big if) you had availability of cellular internet that is probably just as cheap now. However, the landline I had for dialup back in the day had become outright ridiculous in price by the time I convinced my wife we should cancel it (she liked that it worked when the power was out). It seems they don't even want to sell that service anymore.

VoIP is cheap but you need internet for VoIP and I'm not actually sure you could connect a modem to a VoIP even if it wasn't nonsensical.

No, it is not feasible to run modem signals over VOIP, as the various codecs all compress signals and cut frequencies and all manner of things to reduce bandwidth consumption, which are incompatible with modem signaling. You could get away with it in a homelab for fun, but you have absolutely no control over what VOIP codecs e.g. Comcast is running, so it is effectively impossible. Even if the phone company says they can offer you a copper line, your copper line will eventually get converted to VOIP at the end of the street or wherever, and then it's up to whatever commercial provider you're paying to choose the codecs for VOIP, which are never modem-friendly. I worked on this stuff about ten years ago. There are fax codecs but they are very hard to get working reliably.

AT&T used to be the default landline provider for my address, but they recently got the regulators to release them from that responsibility, so now there isn't one. So I can't buy a landline for my property, even though there's copper running right past it and a pedestal where all they'd have to do is reconnect the line to my house. If I call AT&T, they'll sell me a cell phone, but not a landline.

Fortunately I have fiber (from another company), so it's not a problem; but the concept of being able to get a landline anywhere is going away.