I’ve just released a new version of EmonESP V3.1.0 https://github.com/openenergymonitor/EmonESP/releases
The most significant feature of the new update is the lack of SPIFFS. HTML/JS has noe been embedded into the firmware which can be loaded in a single upload which the HTTP update via the GUI now works
There are lots of other changes include a serial debug console to view the ESP and the emonTx serial in real time and send serial commands directly to the emonTx from the web UI
Since the HTTP update does not currently work on the last EmonESP version, this update will need to be uploaded using a USB to serial programmer and esptool. See EmonESP release page linked above for instructions.