The older Overdrive app will be discontinued in early 2023.
Note that the company name is also Overdrive, and the Overdrive content on Libby remains the same as always.
You do not need to create a new Libby account, just sign in to Libby with your library card number and PIN. While you may be able to keep using your old Overdrive app for a while, it won't have support features.
Libby is very easy to install and use, please see our Ebooks & More page if you haven't already installed Libby, and scroll down to the Overdrive section.