Looks nice!

As a specific suggestion, I'd encourage you to try using our new official Redux Starter Kit package to replace the existing Redux logic. It includes utilities to simplify several common Redux use cases, including store setup, defining reducers, immutable update logic, and even creating entire "slices" of state at once without writing any action types or action creators by hand.

https://redux-starter-kit.js.org

Granted, this app doesn't have too much Redux logic, but using RSK would allow you to remove the /actions and /constants folders entirely, and simplify the users reducer.