Hi,
ok, I finally managed to get it running.
I will mention the solution here despite it is more GENTOO specific, but may be I am not the only one using Blender on GENTOO Linux - then it may be of help to others, too.
You don’t need to install the Optix SDK nor anything else other than the nvidia-drivers.
GENTOO does change the contents, which get installed into the system. Do to a feature/bug in the ebuild for the nvidia-drivers, these libraries only get installed, if AMD64 and MULTILIB USE-flags are installed.
You can set MULTILIB for the nvidia-drivers only. This flag is normally used in systems, which support
32 bit and 64 bit binaries. In this case it is kind of superflous, since the libraries are 64 bit only.
The missing libraries are:
libnvidia-cbl.so*
libnvidia-rtcore.so*
libnvoptix.so*
The according version of the driver package in question is appended to the filenames of the libraries.
Presumeable because I am on a 64 bit-only system I couldn’t set MULTILIB.
A simply workaround is to get the nvidia-driver package of the same version which got installed on the system from NVidia.
Then unpack and skip the installation of the package with the following command (here for the version
440.64 of the driver):
./NVIDIA-Linux-x86_64-440.64.run --no-x-check -x
which creates a directory NVIDIA-Linux-x86_64-440.64 with the contents of that package.
Then copy the libraries mentioned above to /usr/lib64/. and do a ldconfig afterwards - both as root.
You do not need to stop X for that, but you should terminate blender in advance.
This is a workaround. This is not a “clean way” to get Optix working.
When the drivers get updated via emerge, you need to remove the three libraries by hand – if the feature/bug has not been fixed in the ebuild.
SInce the nvidia-drivers are the same on any Linux system, this should work on other Linux distros
in an adopted way.
Thanks to all who helped me to find this workaround! 
Stay healthy !
Cheers!
tuxic