Yup, working with Portal. Version is ArcGIS Enterprise 10.7.1 Portal. I'm using a Hosted Feature Service for a file geodatabase, which has one feature class, which has the UTC data in question.
Regarding "doesn't work at all in a Time Aware app", my time field is utilized in a web map, meaning data plays appropriately with a time slider. However, instead of displaying the data as it is stored in the time field, it's converted from UTC to 'local' time in a web map, which for me, is Ohio. I don't want that. I have to display it in UTC time because it's for an app that users all over the world will view.
Secondly, I can't get the data to display at all in the Time Aware app. I go to configure the app, the time slider is there, displaying the same 'local' time data as it did in the web map, but no features are displayed in the map. When I press play on the time slider, it cycles through the data in the same way it would in a web map, but again, no features are displayed.
So, I think I have two problems, and I'm not sure if they're related - 1) the undesired time conversion to 'local' time, and 2) features that do display in a web map that won't display in a Time Aware app.
Ideally, I'd store my time data as UTC, and it would be displayed as UTC. Does that help?