Hello,
Thanks for your help. Frankly I thought I could see a draft of my post before submitting it, so I couldn't go back to add the details. My bad.
The e-paper HAT display is from Waveshare, 7.5" Black and White, custom board based ona ESP32. Specifically, it is the one you could find at this URL:
https://www.waveshare.com/wiki/7.5inch_e-Paper_HAT
I already checked the data-sheet and the vendor is not answering (waveshare chat on their webpage is currently offline and so was yesterday).