This particular package is still missing, not available for download and installation in the GetIt Manager in the latest Rad Studio 10.3.
Without this package, I cannot upgrade my projects to the latest Rio 10.3.
When this package is likely to appear in the GetIt Manager of the 10.3 version ?
Yes. I have resolved it in December last year, thanks to the great advice from our local Embarcadero consultant Nirav Kaku.
His advice was to get the OnGuard library directly from GitHub:
open it in Rio and install it the good ol' fashion way (how we did things before GetIt) .
Yes, I just successfully installed in this manner as well.