When entering my new intranet with Vaadin 8 in IE11. I receive a “I’m sorry, but your browser is not supported” warning. We can click the “Continue without updating” link I’m pretty sure our users will complain about that.
Late reply but in case it is of use to anyone, the easiest option to configure header tags is probably the add-on
https://vaadin.com/directory#!addon/headertags . Alternatively, a bootstrap listener can be used directly, but requires considerably more lines of code.