Sonoff Dongle E: web flasher not working

I have tried all the suggested steps I could find (flashing while holding boot button, using Extraputty etc.) but somehow I keep on getting issues in uploading the EZSP firmware to the dongle. I can upload it, but if I upload a firmware the web flasher still gives me the message “Firmware could not be determined” and the green led remains off. The only way through which I can get the web flasher to detect firmware is if I upload the multi rcpan firmware (after which the web flasher DOES detect the firmware). I however want to leverage the dongle in a zigbee only fashion

I am now a bit in the dark: can I start using the dongle E, or should it be recognized by the web flasher first?