Our webapp is usually accessed using Google Chrome in a windows OS. Should we really need to have a windows OS for this or ubuntu with GUI is sufficient?
AFAIK, Chrome is sandbox from the OS. We are using teamcity and selenium, chrome driver for testing. Our plan is to use Ubuntu with GUI and register it as a teamcity agent, e.g. kubernetes pod if possible
From a generic perspective, web applications should be accessible through browsers irrespective of the underlying os. Albeit, Chrome relies heavily on sandboxing, keeping different processes and applications in separate partitions. This limits the interaction between applications and the OS kernel.
Google's browser-based operating system i.e. Chrome OS stores data in the cloud implementing the idea ..."The browser is the operating system"... which relies on many of the same security features and concepts used by the Chrome browser.
Chrome achieves tighter security through Sandbox feature and should be functional irrespective of the underlying Operating System as Linux systems implements Sandboxing too.
You can find a couple of relevant detailed discussions in: