Unable to recognize device after "adb reboot bootloader"

[haohowareyou]

I'm using Mac terminal, after executing adb reboot bootloader it seems that I can't bring anything up once the screen is black with fastboot devices

I'm looking to root it mainly to be able to use this as bluetooth speaker, and not have to use this as a phone to play music from it but rather passthrough audio from say my iPhone. According to GPT/Gemini this is possible to enable something called Bluetooth Receiver mode (A2DP Sink)?

[MalakymR]

I've had this issue for a while now - cannot get into fastboot via adb reboot bootloader.

Try instead, adb reboot recovery.

On the screen, do not select reboot into bootloader, select "..ter fastboot". The text is behind the bezel so cannot quite read the text. This will bring up fastbootd and fastboot devices works.

[wu21-web]

Try fixing the legacy fastboot detection.
Use a genuine USB cable that can transfer data and try different USB ports. It is certainly better to use a USB2.0 cable.
You can also reset the Macos usb system.
sudo killall -HUP mDNSResponder
sudo kextunload -b com.apple.driver.usbserial
sudo kextload -b com.apple.driver.usbserial
Then enable A2DP Sink (Bluetooth Receiver Mode)
Make sure your device is rooted first.
su
setprop persist.bluetooth.a2dp.sink.enabled true' service bluetooth restart`