I have macOS Catalina 10.15.3 (FileVault2 is enabled) installed with Windows 10 in dual-boot and I was able to sucessfully change the Windows icon, but I can't figure out how to modify the icon for my Macintosh HD drive.
I tried with SIP disabled :
- to replace ".VolumeIcon.icns" inside /System/Volume/Data/ by a custom one - To use the Get-Info box from the Finder and changing the icon from here
The changes are working inside the Finder but not when holding "Alt" and using the Mac Startup Manager..
Is there a proper way to achieve this?