That package is part of a repository that isn't available on the Euclid. Some of the packages in that repository are packages that are not compatible with ARM processors, and although the Euclid has an x86 processor and is compatible, it shares some aspects with those types of dev kits. I'm not sure if it's rightfully unavailable because it's unsupported by the system architecture, or if it's possible to use those packages.
We're currently exploring options to see if this is something that can be made available.
In the meantime I'd recommend installing RTAB and other packages from source, if possible, via github or the like.
Intel Euclid Development Team
I have had a lot of luck lately connecting to the general ros repository per instructions from their website.
This allows getting the latest updates but you MUST be sure to hold back the package "ros-kinetic-realsense-camera".
That is a special build of the package for Euclid and you cannot install the generally available package or you will probably need to re-install your image (been there!).
Holding back a package is pretty simple:
sudo apt-mark hold ros-kinetic-realsense-camera
I got the information from here: updates - How to prevent updating of a specific package? - Ask Ubuntu
The instructions to point to the ros repository are here: kinetic/Installation/Ubuntu - ROS Wiki
It just takes a couple command-line copy/paste from the website. I don't recommend doing a full desktop install. Just install packages as needed.
I've been installing gobs of packages as needed and have had no problems so far.