I can only speak for Deus ex: mankind divided since I have played that myself.
It is technically a sequel in the sense that there are other Deus ex games that came before it with the original Deus ex, invisible war and human revolution. That said every single one of those games has it’s own self contained story with only some overlap between them. Mankind divided features the same main character to play from the previous game but everything else is different. From the location to the characters barring one which isn’t an issue for reasons… And is also otherwise completely isolated from the first two games maybe with one Hommage that you might miss If you don’t know the first game but then it’s just a great character instead of the thing it’s supposed to be.
Long story short, IMHO you can just pick that one up and play it without worrying about missing a ton.