Anyone finding this question and wondering if there is now support in Vaadin, yes there is. Vaadin 24.5 has introduced the Popover component (https://vaadin.com/docs/latest/components/popover), which has multiple uses. In this context, it can be used as a rich text tooltip. It can also be used as a context menu, notification or dropdown field etc.

Note that https://vaadin.com/directory/component/tooltips4vaadin is essentially discontinued as the developer no longer works for Vaadin.