Stable Couchbase version for Ubuntu 16.04?

Is there a stable version for Ubuntu 16.04?

Couchbase 5.0 - which is currently in Beta and expected to GA later this year - will add official support / DEBs for Ubuntu 16.04.

Having said that, I know a number of people have used the Ubuntu14.04 packages on 16.04 successfully - so you might want to give them a try.