Your easiest bet is to use the "node-red-node-ui-iframe" node, it even has options like the page scale and origin built right into the config editor. In the node's config, enter "http://test.local:1880", and assign it to a dashboard tab and group like normal.
Did you check that the page loads on a browser on the same machine that is running Node-RED?
It looks like the remote device (the alexa) is not allowing the iframe to connect, it is saying "connection denied by test.local" not "unreachable"
Another thing you could try is setting the origin in the iframe settings to a user agent of a common browser, for example: "Mozilla/5.0 (platform; rv:geckoversion) Gecko/geckotrail Firefox/firefoxversion"