tERBO

@raven123 yes, I moved rockchip64 edge kernel to 6.10 and brought in the patch to fix the gpio2 bank that was causing the whole eMMC issue.
BTW, packages should be available in the near future when the armbian server will rebuild the things (hopefully, next sunday)

Yesterday a lot of measurements were added to the GIT for the Rockchip family.
I rebuilt a new version with kernel 6.6.41.
And eMMC started to be detected correctly.

@tERBO Something worked!   

I flashed that image you shared.  It was not promising; as the VFD display was not working.   
 
I redownloaded Multitool and a different Armbian image from @jock's stable folder and flashed a different microSD using a different computer.  

Happy to report that I have a live system now!  I wish I had asked sooner before wasting nearly a day going in circles!   Thanks for the assistance - was nearly ready to send this board to eWaste recycling.  

ADVICE
 
@tERBO discovered, at his expense, that upgrading the kernel to v6.6.38 breaks the eMMC support (see his thread), so please do not upgrade the kernel until the issue is solved!
The issue seems related to some patches that have been mainlined in the kernel, but further inspection is needed to be sure what is causing the problem.

@tERBO
Here it is, kernel 6.6.38 and emmc broke on my system too:
 

 
I will try to revert some patches mainlined patches in the next days to see if it fixes something. The rk3308 should be quite different than rk3318/rk3328 and the commit was limited to rk3308-rock-pi-s, so I don't think that's the issue.

The same problem when building the image yourself using compile.sh and installing from it.
I made images today with default kernel settings:
Armbian-unofficial_24.8.0-trunk_Rk3318-box_bookworm_current_6.6.38_xfce_desktop.img
Armbian-unofficial_24.8.0-trunk_Rk3318-box_bookworm_edge_6.9.8_minimal.img
Both of them show this problem.