Really sad but not unexpected. Development had stopped 1 1/2 years ago (though there was one minor bugfix in late 2021 when search functionality broke), the last major version released to commercial customers (v8.7.0) was in 01/2019.
Some people claim that development continues behind closed curtains, I for one think this is a lie (I’ve seen the same lies at Scalix before I had to migrate to Zarafa, then Kopano) but of course it COULD be true. But even if they come out with a new commercial-only version, I would not be interested. A software without a public discussion forum is worthless to me, the commercial support is usually staffed by people with only the minimum knowledge possible to get the support job and they don’t really have any clue because if they had any clue they would work in development not in support.