Are you using the latest chrome version i.e. 83.0.4103.61 ? It seems the latest chrome version causes similar issues. Can you try using a different browser to verify ? The issue I am referring to is under investigation via GRANITE-30226

If you are connected as a user with proper access then enable the browser debug to verify if there is any error in the page ?

You should be able to overlay the existing component to configure your style in RTE. The following article help you for this:https://helpx.adobe.com/experience-manager/using/touchUI_RTE_configure.html

This doc can help you with this requirement:https://docs.adobe.com/content/help/en/experience-manager-65/administering/operations/workflows-managing.html#configuring-access-to-workflows

It's true .. it seems its not possible to achieve this via permission restrictions.

Can you verify if can do it via ACLs for individual path in crx/de ?

If its not announced in technical requirements then its not supported yet. It does not mean it will not work. It means it has not been yet tested and not officially supported until its tested and publicly announced.

You can use a custom rendering condition to overlay the standard action and impose specific conditions that must be fulfilled before it is rendered.https://docs.adobe.com/content/help/en/experience-manager-64/developing/extending-aem/customizing-consoles-touch.html

Are you using the latest chrome version i.e. 83.0.4103.61 ? It seems the latest chrome version causes similar issues (package upload failure). Can you try using a different browser to verify ? There is a JIRA opened to further investigate the issue.

Per the shared doc archetype 22 is supported in AEM 6.4 so I do not see why you can not use it ...