For the past 2 release sets we were releasing ARM packages from the Foundation buildbot. 10.3 and 10.4 releases of CentOS 7 aarch64 don't contain Cassandra, and there are no signs in the compilation logs that it is being built.
Other platforms, e.g. CentOS 7 amd64, have the packages, so it doesn't look like it was discontinued on purpose.
Starting from 10.5, we don't build it anywhere (intentionally).