One approach could be to use a microcontroller like an ESP32 that supports BLE and WiFi, or even a Raspberry Pi, and have code running on there that scans for BLE advertisements and POSTs them onto a REST service in your Mendix application to process.
This would mean some custom C, Python, or other supported code to handle the Bluetooth reception and posting though. Those microcontrollers are pretty cheap and run from USB power. Once programmed you can run them with power from an old phone charger.
While I’ve not used BLE, I have used this approach myself for taking sensor readings and POSTing to a Mendix application.
Hope this helps.
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