I second that request.
I've been trying the bluetooth connection on the linux side with bluetoothctl. I connect, but shortly afterword it disconnects. I was able to query the GATT characteristics, but still didn't get anything. I added BLE passive under HACS in HA, tried looking for devices, nada.
I found
https://github.com/tfyoung/esphome-junctek_kgf/tree/usesetjmpfix/components/junctek_kgf using esphome to rs458, have the parts and flashed it, but haven't connected to the junctek yet as I wanted to try the bluetooth.
On their youtube videos, I saw Junctek mentioned passcode BTG010 as a note. When connecting with the app, it usually search and connects directly but I used phone bluetooth to connect manually with the code and it said "an app is needed".