Unfortunately it is what @Lin-Buo-Ren wrote. I would suggest to contact AMZN2 support and asking about the possibility of adding snapd to the extras repositories.
Amazon Linux 2 can install some packages from EPEL7, but not all of them. Snapd is EPEL is built with SELinux support, but AMZN2 does not ship the policy packages that the EPEL rpms are built with.
In the meantime, you can grab the source tarball from snap releases page right here: https://github.com/snapcore/snapd/releases/download/2.47.1/snapd_2.47.1.vendor.tar.xz Extract is somewhere, and the packaging/amzn-2/snapd.spec has all you need to build the RPMs yourself. You will need to copy the tarball to ~/rpmbuild/SOURCES (or set the _topdir accordingly).