Yes of course, you have to select an esp8266 device...
... which does not appear on the "Device" selection page.
Essentially, it will not allow me to select the ESP8266 as both the "Device" and the "Module", and assumes that the ESP8266 is a "bridge" module to a "device", rather than it being the target for the downloaded app.
The closest I can get to a configuration which gives me the "Apply" button, is to select the "Device" as an ESP32 board, and the "Module" as "WiFi on chip".
This gives me this configuration...
// RemoteXY select connection mode and include library
// RemoteXY connection settings
#define REMOTEXY_WIFI_SSID "RemoteXY"
#define REMOTEXY_WIFI_PASSWORD "12345678"
#define REMOTEXY_SERVER_PORT 6377
.... which does not work with the ESP8266
Everything works with smoke - if you let it out, things stop working....