[Renate]

I'm drawing a blank.
I can identify many of the test points, but I don't see anything unless it's close to the battery connector.
This is a shot of my Poke3 (same SDM636) to show you how obvious they made it.
The glass reed switch is my addition. The UART is on the (also added) white connector.

You can try disconnecting the battery and reconnecting, see if anything changes.
That's on a "mezzanine" connector. You can pull it with your fingernails on each side (knuckles against the board). Pull evenly on both sides.

While the battery is disconnected, you might look under the Eink panel connector.
Manufacturers try to be sneaky sometimes.
It's a mezzanine connector too.

If your device WAS working it would be easy to find the EDL points. Since it's the same SDM636 I know that it's GPIO57 and even have a program for detecting it.

I think that you have to get a resistor or two. Got any neighbors?
If you had a 1000 ohm and a 1.5V battery you could just test all the points.

P.S. If you look under that Eink flex don't bend it too much.

P.P.S. You're really, really sure that holding one of the buttons while resetting doesn't get you to fastboot?
My Poke3 doesn't have any buttons.