Help with 3 way wiring in old house (No neutral)


So I recently just bought a house and am planning on upgrading most of the switches to inovelli switches. In this specific example I plan on getting one of the new blue switches with the mm wave detection that are on pre-order right now alongside an inovelli aux switch. I also forgot to take photos of the switches when I was visiting the new house earlier so all I have at the moment is this infographic that I’ve drawn of the situation. I’m hoping that’s enough to go off of at the moment but I can provide more info/images next time I’m over at the house.

Anyway, I’ve got a light with one switch at the bottom of the steps and another at the top of the steps. This is how the switches are currently wired up:

I’m assuming that the wire coming from the bottom of the 1st floor box is the hot wire. This wire IS black, it’s the only one that I remember for sure being black. And the wire coming out of the top of the 2nd floor box goes to the light I’m guessing. I’m also assuming that there are no neutral wires but perhaps someone could tell me if I’m wrong or not. There’s no ground wire in the box and no other wires either.

Based on some looking at other forum posts I’m thinking this is what I need but I was hoping somebody else could chime in on this.

Any help is greatly appreciated and if you need more info let me know what you need. Thank you!