In the Linux (Ubuntu) desktop app, outbound links say they will open in the default browser, but actually always open in Chrome (which is not set to default on my system). For links in the body of an email, it is possible to copy the URL and open it manually, which is less-than-great user experience but at least provides a workaround; but for system links (such as when the desktop client has an upgrade available) no copyable URL is provided.