My situation: I have finished university more than 10 years ago. I work for company X. I also own a small startup company called Y (no employees). I am in the process of publishing a paper and I was asked to provide an affiliation. Not providing one is not an option, in the sense it's a mandatory field on the form. I asked X and X said no, as I worked on the paper in my spare time.
Does it make sense to use Y as my affiliation (which is 100% true though not necessarily relevant)? The other option would be to try with something like "Independent researcher" and hope the journal is fine with it (idea came from here; example).