Yes, the best option here is
[env]
OAKAPP_STATIC_FRONTEND_PORT = "8080"
For context: oak-agent (the service that runs your app) automatically picks a free port in the range 9000-9128 and puts it into OAKAPP_STATIC_FRONTEND_PORT env var, which your app then uses.
If you hardcode a value in the env section, you override this assignment. That's ok as long as your device is only running a single app, so you're not risking port collisions.