Back on High Sierra when I wanted to tether my MacBook Pro to my iPhone and save some battery power, I used Bluetooth and chose “Connect to Network” through the Bluetooth icon up in the menu bar. In Big Sur, that changed: when you go to the Bluetooth menu and choose your iPhone, it briefly connects and then disconnects.

I found that the “Connect to Network” option is now buried. Assuming you’ve already paired your iPhone via Bluetooth to your Mac, you can enable Bluetooth PAN using the following:

1. On your Mac, open “System Preferences”.
2. Click “Bluetooth”.
3. Right-click on the name of your iPhone and choose “Connect to Network”.

You’ll now be tethered to your iPhone via Bluetooth PAN. I only do this when I have low bandwidth needs and plan to stay tethered for a long time on battery power. In limited tests with speedtest.net and a tethered Bluetooth connection on Total Wireless, my macbookpro12,1 gets about 0.75 Mbps up and down. When tethering via wifi, the bandwidth jumps to about 40 Mbps down and 7 Mbps up. Finally, tethering via USB was nearly the same as the wifi-tether, although via USB the ping time dropped by 10 ms. This is with crude testing of one sample run for each connection type.