OK, thanks for the background, Ethan!
UBAQs are what we used before functions, and they still have their place for certain scenarios like Dashboards with mass update. Epicor Functions are C# code that can be exposed via REST. The Kinetic browser uses REST to communicate with the server, and we want to do the same.
@jgiese.wci and @josecgomez wrote a browser-based trace utility that you should check out. You can also look at the network tab in the Chrome Developer Tools (F12 in your browser as you probably know).
So, as a React programmer, would you like to define the API that you’re calling or do you like to figure out what the hell some programmer you’ll never meet was thinking?
IMHO, always use REST, and define your own API via functions. There are lots of examples here to help.
EDIT: If you are at 10.1.600, you won’t have functions. 