I think most or all of them have AI, so in general, yes, at least a few are. The only ones I can vouch for having played solo are Terraforming Mars (it has a race-the-turn-clock mode I think, along with AI players) and Dune Imperium, if you like getting your ass kicked by robots.

I think the social aspect is one of the best parts of board gaming, so playing solo can feel kind of lonely to me, but it’s definitely a common feature. Async is my favorite though, because you can wrangle a group of friends to play a game over the course of a few days during everyone’s free time. Sometimes everyone ends up online at the same time and you’ll knock out half a dozen turns, other times you’ll do a turn or two in a day.