Signs a guy isn't over their ex?

[Datingonline]

I'm meeting guys through online dating and some are clearly not over their ex.
However there are also some who are not over their ex but hide it which means the signs are more subtle.
What red flags should I be looking for that a guy is not over their ex?

That they don't have an amicable relationship with the ex?

That they haven't let much time pass before looking for a new relationship. Suggests they are looking for someone to fill the gap, or a 'rebound'.

On online dates ive been on, the first timr they criticise their exwife and mother of their child. Also ive heard a lot of their wife had 'mental health' issues. After two hours I could generally guess why...