Ok I've got some news. On High Sierra I successfully activated handoff, continuity and unlock with Apple Watch. I applied this
https://forums.macrumors.com/threads/imac-mid-2011-bluetooth-4-0-internal-upgrade.1780242/page-13 post #309)
In terminal get your board number using the following command: ioreg -l | grep "board-id" | awk -F\" '{print $4}'
For example my board number is: Mac-942B59F58194171B
Using TextEdit search for your board number (i.e. Mac-942B59F58194171B) and set flag to "true" in: /System/Library/Frameworks/IOBluetooth.framework/Versions/A/Resources/SystemParameters.plist
Note: First copy SystemParameters.plist to your desktop, edit it, and then copy it back into the /System/Library/Frameworks/IOBluetooth.framework/Versions/A/Resources/ folder. Keep a backup copy of the original SystemParameters.plist file in case you need to revert back to the original
Then perform these two commands in Terminal:
sudo -E perl -pi -e "s/\Mac-00BE6ED71E35EB86/\Mac-942B59F58194171B/" /System/Library/Extensions/IO80211Family.kext/Contents/PlugIns/AirPortBrcm4360.kext/Contents/MacOS/AirPortBrcm4360
sudo -E perl -pi -e "s/\Mac-00BE6ED71E35EB86/\Mac-942B59F58194171B/" /System/Library/Extensions/IO80211Family.kext/Contents/PlugIns/AirPortBrcmNIC.kext/Contents/MacOS/AirPortBrcmNIC
In system preferences/general: Uncheck "Allow Handoff between this Mac and your iCloud devices"
Reboot
But on Catalina I can't do the same procedure because I can't modify file system in /System/Library/Frameworks/IOBluetooth.framework/Versions/A/Resources/ folder.
Someone have an idea to do this ?