I am also interested in this, as I am currently working on a wrapper to bring ConverseJS (XMPP client) to UT.

Looking at this repo: https://github.com/florisluiten/rssreader/

There seem to be some built in UT styles:

<link href="/usr/share/ubuntu-html5-ui-toolkit/0.1/ambiance/css/appTemplate.css" rel="stylesheet" type="text/css" /> <script src="/usr/share/ubuntu-html5-ui-toolkit/0.1/ambiance/js/fast-buttons.js"></script> <script src="/usr/share/ubuntu-html5-ui-toolkit/0.1/ambiance/js/core.js"></script> <script src="/usr/share/ubuntu-html5-ui-toolkit/0.1/ambiance/js/buttons.js"></script> <script src="/usr/share/ubuntu-html5-ui-toolkit/0.1/ambiance/js/dialogs.js"></script> <script src="/usr/share/ubuntu-html5-ui-toolkit/0.1/ambiance/js/page.js"></script> <script src="/usr/share/ubuntu-html5-ui-toolkit/0.1/ambiance/js/pagestacks.js"></script>

But they look a bit unfinished. Given that it says version 0.1, I am wondering if there is maybe a newer version available by now?

Edit: This seems to be similar: https://youtu.be/g5pD3b87bC4

Edit2: this seems to be the latest version and Ubuntu seems to have stopped including this in distributions later than 16.04. So for now it will work, but I guess once the switch is made to 20.04 these will need a new maintainer.