He would have put troops in Ukraine and told Putin if you attack them we would attack you.I'm going to take the contrary position. Trump was a strong man; this is obvious. However, it was equally obvious he was being consistently and publicly undermined by his own government. Additionally, the narrative is that Putin is a power hungry lunatic- people who are not of sound mind make irrational decisions. So, yes, given these two points I think we'd still see an invasion of Ukraine.
The real question is what would a Trump administration have done in the face of this invasion?
Putin isn't going to rosk NATO involvement