I?ve seen this issue on multiple forums with no real answers. Bluetooth is dead not showing a interface at all. I was having this issue myself with both a 3b and a 4b 8g model with both 32bit and 64bit fresh installations of Kali 2021.3. The solution I found is adding the following line to your /boot/config.txt dtoverlay=enable-bt save it and reboot. Hope this saves you some time and headache
