If you're using Sessionize for your event, you can use the app pretty easily. Customized config is kind of spread throughout the app. Primarily you'll need to point to your data urls, change the data seed files for speakers/sessions/sponsors, and change the color settings.
The UI is in the process of being fully ported to Google's Material Components, with a centralized color and font theme. That's a work in progress, but eventually you should be able to modify central files for Android and iOS to provide for a specific look.
It would be super great if you could keep us in the about section of your app, though. We're a consulting company that turns project revenue into open source stuff, so we need eyeballs. Thanks XOXO. Speaking of...