Tawk.to is not bad, but there have some issues around it. The plus of the tawk is that is free and you can add some addons from their platform. It has mobile and desktop application.
What issues have you noticed?
For example, sometimes the mobile application has some slow reactions. it doesn't ring when there have a chat started by a client. From last update to now is okey, but that is not nice when you are not at the office and want to look at the chat at the same time. The desktop application do not have issues like that.