Ok good. Only you can determine what you have. Hard to do with certainty here.
But if you do have the configuration in the last drawing I posted, here is the solution. This has to be a dimmer since it will be a non-neutral.
In that drawing, a hot without a neutral gets sent to one box. The Aux switch goes in that box. The hot gets connected to the neutral terminal of the Aux (because in a non-neutral Inovelli config, that’s what it needs).
When you use an Aux, you need two conductors over to the Inovelli. So you will use the equivalent of the red and the white for that. Cap off the unused conductors.
The Inovelli goes in the Load box as a non-neutral. The hot and traveler come over from the Aux (via the light box). The Load is in that box.
Don’t forget to set the parameters for non-neutral and 3-way momentary.
And you or your electrician should fix that lack of grounding and ungrounded boxes. It’s important!