Not really an app. Go to View, then Toggle Developer Tools. Looks the same as Chrome.
Chrome version: 69.0.3497.128
How is it better then using Chromium? My Chromium is newer.
You can load localhost, if you have a webserver running. Put it in an iframe.
You may be able to get it to load something else by editing /etc/hosts. But then you will most likely send your login info to some other server.
I removed Zoho Mail Desktop, don't see the point in it. Works just as good in a browser.