Failed to connect to peripheral <my mac address>, addr type: random about bluepy

[dieser-niko]

Not an expert but have you tried to use public address type?
peripheral = btle.Peripheral(mac_addr, addrType=btle.ADDR_TYPE_PUBLIC

Also if possible, could you share a code snippet?

[doug-holtsinger]

I have code that works with a Pi3B as the Scanner and the nRF52840 Dongle as the Peripheral.
Scanner Connect: https://github.com/doug-holtsinger/WirelessSensor/blob/master/Compute/src/AHRS-VISUAL/ahrs-console.py#L703
Peripheral: https://github.com/doug-holtsinger/WirelessSensor/blob/master/Sensor/src/BLE/ble_svcs.cpp#L771
I had to workaround a connect problem by limiting the MTU size on the nRF52840 to 23 bytes, otherwise it would not connect. The Pi3B was sending out garbled packets during the connect phase. Do you have a Bluetooth sniffer? It helps a lot for diagnosing connection issues.