They are not supported. MacOS is special and, while not supported, is almost certainly going to work fine because lots of folks develop on MacOS.
Not supported means some fairly specific things from a legal perspective if you have a contract with Elastic and from a "if you open an issue about it we won't fix it" perspective. But it usually doesn't mean it won't run. At least for Elasticsearch. It might not run and if it doesn't we won't be able to help you with it. And we might break support for it in a minor release because we don't test against it.
But, as a practical matter, at least modern versions of MacOS are almost certainly safe.
If you want to prototype something against elasticsearch and it runs ok then, I'd say don't worry too much about it. If you are thinking of basing a project on Elasticsearch that has to run in Windows 7 or something then I'd stay clear.