I've had a LOT of difficulty bridging the gap between React Native BLE PLX library and the NRF52840 board in terms of sending data from a phone app to the board.

After a bunch of looking around, it looks like I'll have more luck finding examples for an ESP32 based board, such as this awesome writeup: https://www.cjoshmartin.com/blog/bluetooth-low-energy-ble-with-react-native-and-arduino

I'm going to try to set up a "characteristic" that I can then "write" to so that I can send a packet of information to the device.

And while I'm not sure, it looks like the timer I had running on it previously with no issues stops after 2 seconds on the Adafruit ESP32-S3 board.

I will update when I have news!