For email I think the best choice is still M365. It’s not free and not self hosted but IMHO it’s by far the best e-mail/collaboration suit that exists

Do you mind to explain when to use Helm charts and when to use standard deployments? You said that they are useful for more complex deployments, why is that?

Don’t have any idea on how to implement it IMHO you need to add some kind of support for e-readers like Kindle and etc. Some people read on theirs PCs but the reading experience it’s much better on readers devices.

Idk, but is available to download and install

No problem so far. Working perfectly here.