I tried out using Vaadin, but I decided to not using it. My main point for deciding against Vaadin is that when Javascript on the client is disabled then no content at all is shown at the page, not even the static parts of the page. I instead want my webfrontend to be as usable as possible even when Javascript is disabled.
So I will instead try a first simple demo implementation using Thymeleaf and Server Sent Events. My idea is to generate the HTML of a page on the server using Thymeleaf, containing all the dynamic information that is available on the frontend at that time and embedding a simple Javascript function into the distributed HTML that registers to a Server Sent Event endpoint on the frontend where updated parts of the HTML are pushed to the client when information has changed.
That way, with Javascript enabled the web client is receiving real time updates from the server as soon as new information is available, but if the client can not execute Javascript the user just has to refresh the page to see new information, because the client still receives a whole updated HTML page on the pages refresh.