The use of these tags has changed. Instead of
joomlacontentyou now use
article(for manual selection or
autoarticle(for categories). You can use these in the html editor.
Adding articles in the drag & drop editor has become much more easy. You simply drag the Joomla Article content block into your email and select your articles manually, by category or by tag.
It's documented here: https://docs.acymailing.com/addons/joomla-add-ons/joomla-articles
Inserting content from jDownloads is just as easy. All you have to do is to add the jDownloads add-on to your Acymailing. You can do this in Acymailing->Add-ons->Available add-ons. Once done you get an extra content block in your editor that you can use in a similar way as the Article add-on.
The jDownloads add-on is documented here: https://docs.acymailing.com/addons/joomla-add-ons/jdownloads