It depends on the maturity level and mutual respect of the people involved. When I refer to the people, I mean both the ex's and the new partners. So, it is possible. I've done it and it's a red flag if the new person I'm with lacks the maturity to be able to handle my ex as a friend in my life because, at my age, I just don't want to deal with that level of insecurity and/or jealousy in a romantic partner. When that starts to happen, it's like "Next!"
However, I think if an ex cheated, that definitely muddies the waters and can just erase that possibility for most people. Even so, I know a lady who was married to one guy, cheated on the guy with the guy's brother, and yet, despite the lady and guy getting divorced, all three remain friends. At first, I thought this must be for the benefit of the kids but the kids are all grown up and have moved out. Yet, the three still spend time together socially as friends and she is even remarried. The new husband is okay with all of it and hangs out with all of them, too. So, if everyone wants it, it's possible.