So I realized that the reason people have gaps are always pretty much wildly private reasons, often those that can cause discrimation such as revealing health issues etc, mental health struggles, family drama, etc, illness in the family, it can reveal your marital or parenthood status. It really should be one of the questions HR tells people not to ask due to legal issues, such as age, sexual orientation etc.
They're almost always deeply personal issues, that are not appropriate to discuss in a professional setting. If the employer is worried there is some kind of incarceration going on, they can ask that question directly. I'm sorry, I am not discussing the real reasons for my work gap with anyone other than my partner and my therapist, because they're so personal. I don't want to feel like I am forced to lie either.