This is something I’ve only had happen recently, but right below the title bar is a line of blue text that says “You are using the testing theme” like so:
And it stays there when I scroll down:
It’s there in the mobile app, too:
I’ve been using the test theme since the “Display OP” feature was put there, but I’ve only started seeing the test today. So, I have to ask: is that supposed to happen?