BT Learning Lab (Bluetooth communication learning app) is a developer-oriented learning app that allows you to learn about Bluetooth and BLE communication with electronic scales, printers, and e-paper devices while viewing actual packets and logs.
Decent Scale (BLE scale)
SM-S210i (StarXpand SDK compatible printer)
Gicisky 2.9" E-Paper (HTTP → ESP32 AP → BLE)
This is a developer learning app that allows you to learn communication protocols using actual devices such as Bluetooth/BLE printers and e-paper.