You can try Headkaze's updated version for Catalina or Mieze
https://github.com/headkaze/OS-X-BrcmPatchRAM/releases
https://www.insanelymac.com/forum/topic/339175-brcmpatchram2-for-1015-catalina-broadcom-bluetooth-firmware-upload/?do=findComment&comment=2692431
Just need BrcmBluetoothInjector.kext, BrcmFirmwareRepo.kext and BrcmPatchRAM2.kext in /L/E
Repair permissions and rebuild cache as always.