Search for the snap:
$ snap find cassandra
Name Version Developer Notes Summary
cassandra 3.7 ev - Cassandra distributed database
Install the snap:
$ sudo snap install cassandra
[sudo] password for elopio:
cassandra (stable) 3.7 from 'ev' installed
Check the status:
$ cassandra.nodetool status
The status check fails with:
nodetool: Failed to connect to '127.0.0.1:7199' - ConnectException: 'Connection refused'.
The snappy-debug tool shows many denials: https://paste.ubuntu.com/23414838/