Nonsense business strategy… Isn’t it?
In the NGINX pre-built official packages, the Brotli module is only included in Nginx Plus, not in the open-source version, as if Brotli were a premium feature and not an open-source project.
On the other hand, the Cache Purge module is a premium feature included only in Nginx Plus. However, you can find a similar module included in Debian and Ubuntu Nginx packages, and it appears to be promoted by the Official NGINX channels.