If you watch eSports broadcasts (especially from Asia), you sometimes see the audience showing a scrolling messages on their mobile phone. I wanted that app for a while and haven't been able to find it until recently. I had used text scrolling as the search words and had no luck, and finally trying LED text by chance hits the jackpot.
If you still have no idea what I'm talking about, here is a Youtube video I find of it in action: https://youtu.be/yaC7Inn1cUc?t=154.
LEDScreen is the app I end up with, and if you enter that word into the Google Play Store, or use this link, https://play.google.com/store/search?q=ledscreen&c=apps&hl=en_US, you get the following:
My app is from the Xiaomi App Store because I have a Xiaomi phone. So as you look over your choices in the Play Store, do review the comments and app permissions.