Surprisingly, Facebook has anticipated this exact situation and has made it a simple process to keep Messenger while sunsetting your Facebook account. Facebook is Here to HelpOddly enough, all the things that you need to consider when quitting Facebook, the service gathers together for you. Now, in the web interface (since you already deleted the app) go to Settings > Your Facebook Information. If you still need Messenger, you can click the Deactivate Account button. I'm of the mind that if people want to connect with me on Facebook, I'm not going to cut them off from that.

Source: Forbes January 13, 2019 13:07 UTC