Is there a way to expose the server metrics such as the ones under the Metrics Dashboard to a third-party app such as prometheus?
Did you mean to post this under the module development category?
The answer is that there’s nothing immediately accessible (though this is something we’re interested in doing first party), but there’s nothing stopping you from writing a module to do this. In your module hook’s setup invocation, you’ll get a GatewayContext object that has a MetricRegistry getter:
https://files.inductiveautomation.com/sdk/javadoc/ignition81/8.1.19/com/inductiveautomation/ignition/gateway/model/GatewayContext.html#getMetricRegistry()
If you have WebDev Module, it isn’t too bad to put together a simple metrics endpoint that Prometheus can consume via scrape_configs. You’d just use the python resource in WebDev and return a GET payload in the Text-based exposition format.