Well after 6 months I managed to figure out that the Github team on epsonscan2 software will not get involved on old scanners.
https://github.com/flatpak/flatpak/issues/5603
and after several months I did write to the indicated Github group:
https://github.com/flathub/net.epson.epsonscan2/issues/14
and I have got a response that it will not be planned supported any more.
Its a pity since the non flatpak version I am sure that it did support my scanner (Perfection 4490 photo) via usb connection. I still do not understand why to drop it out. Marketing reasons or package size?