There’s a red “1” notification on the Settings button at the bottom right, but I have no idea what it is.
Clicking on the button just opens Settings, no markings saying what the notification is related to.
Poking around a couple of settings didn’t reveal anything.
On Android, v2.24.0
FIXED - It was a notification that an upgrade was available.
What’s also funny is that there is a person asking exactly the same question in the screenshot that you shared
I approve of this message.