Does somebody have a manual / jumper setting for this card? Otherwise I will report here what I find out.

The ET4000AX is labeled "P/N:2140"

Its this card:
https://theretroweb.com/expansioncards/s/unknown-2140-rev-c

Its interesting because it has EGA and VGA out. And the ET4000 should be a fast card.

I dumped both ROMs:

This is not a product of IBM (IBM is a trademark of International Business Machines Corp.)
Copyright(c)1988 Tseng Laboratories, Inc. 09/14/90 V8.01
Enhanced VGA BIOS MODEL:2140. 09/14/90

I got the card with all 4 DIPs "OFF". When powering on, VGA-out shows a a sharp and crystal clear picture on my DELL LCD, much much better than a more modern PCI-VGA.

At the same time, BIOS screen is output on the digital EGA-connector!