Big Sur Bluetooth automatically connects

It might have been the Logi Options application which had access to Bluetooth. Removed the permission and it seems like this issue doesn't happen anymore.

EDIT: nope it's not the Logi Options app. Still happening for some reason. Also I have Handover turned off.

The address changes time to time and automatically connects to it. WTF?!

70-b6-6c-3a-30-d2:

Address: 70-B6-6C-3A-30-D2

Random Address: Yes

Resolvable Address: Yes

Services:

Paired: No

Configured: No

Connected: Yes

Bluetooth Core Spec: 1.0b

Class of Device: Low Energy

AFH: On

AFH Map: fffd0f801b

RSSI: -62

Role: Peripheral

Connection Mode: Active Mode

Interval: 0 ms

It took my a couple of days until I figured out what was happening with my Macs BT.

First of all it has nothing todo with MX Keys Mouse / Keyboard. There is a bluetooth devices which was once paired with the Mac but somehow (maybe you manually deleted the paired files on your mac) lost all the paired device list. The unknown BT device was still "paired" with the Mac.

You need to find out what device connects to your Macbook. When that strange device is connected to your Macbook run the following Terminal command line before it's disconnected : system_profiler SPBluetoothDataType

This will print all the devices which are paired and connected to your Macbbok. From here check the unknowns BT ID. Look at the "RSSI: " which represents the strength of the BT connection. Compare these values with your MX Keys/Mouse and try to guess how far the unknown BT devices is. After you guessed it you need to remove / repair your device to your Macbook Pro.

In my case, I did reset all my BT connections on my Macbook Pro (deleted some paired files, reset BT connections, all the things that I found on other forums) but my IPhones BT pairing was never reset. So my IPhone tried to connect to my Mac. This caused to drop my other BT connections. I noticed time to time the MX Keys Connections were dropped once I unlocked my IPhone. The RSSI signals values were pretty close to my MX Keys. Moved my Iphone in the room (before losing the unknown BT connection), run the command line again and noticed that the RSSI values were much bigger compared to my Keys so I knew it was my Iphone. On the Iphone there was no paired entry in the Bluetooth Settings, this confused me even more. The only solution I had was to reset my Network Adapter/Settings on my Iphone (Reset your Network Settings. Tap Settings > General > Reset > Reset Network Settings) this removed the invisible Mac Paired and all my Wifi saved passwords.

In other cases it might be other IPhones or even other bluetooth devices. Try to rule out all the BT devices that are near your mac.

Hope this helps in your debugging. Happy new year!

You might have a different problem. It's really hard to debug these BT issue. It took me days until I figured it out. The most annoying thing is to figure out what device is trying to connect.

You can also try to turn off Handoff on your MAC.

Here are some potential fixes: https://macreports.com/fix-bluetooth-problems-in-macos-catalina/

Try to disable handoff, maybe this works.

If that doesn't work try to isolate what BT device tries to connect to your macbook. Keep in mind that your Macbook doesn't know the devices name so just the ID is printed. The "rogue" device once was connected to your makbook.

Probably an Apple device like IPhone, Ipad, or maybe a different device. Try to roll out one by one the devices in your room, for instance Disable all BT devices which are not used anymore with your Mac or just move all BT devices far away from your macbook.

In my case it was the IPhone which was connecting to my mac, I never manually paired it to my mac, it's Apple magic. I noticed the BT connection drop when I was unlocking my phone.

If you have the nerves you can try to reset the "Network Settings" ("Reste Network Settings") on your IPhone/Ipad/... This will wipe all saved Wifi passwords and all paired BT's. You will need to type your passwords for your Wifi and re-pair your devices. This is what it worked for me but I can't guarantee it will work for you.

I still think locating the BT device is the best option. With the system_profiler SPBluetoothDataType command line you can identify the signals strength and pinpoint the Unknown BT Device location based on the RSSI value . (Eg check MX Keys/Keyboard RSSI vs the Unknown device Signal).