[MTCD Software Development] GigCSburger:
So I downloaded SD_Firmware_Tool from the location mentioned by opexo above, and voila, I was able to boot into Nougat. I had to try different USB sticks with the images downloaded at different times, and one of them finally worked, and now I have Android 7 installed on my HU Eonon GA6200F! Am I happy now!

I was super-surprised how fast it was! I connected to internet via my phone and logged into Google account, and it slowed it down considerably though. Then I activated MicroG and the HU got snappy again! And let me tell you, I have never seen it so fast! Not a day since I bought it four years ago. I also noticed that the screen became brighter, sure the color scheme is different, but still it is visibly brighter and maybe somewhat crispier, not sure, but something changed.

I installed jetAudio+, MX Player Pro and Torque from SD card with no issues. The sound is great and even greater than it used to be before. Maybe this is due to the fact that the versions of the apps installed are more recent. MX Player that I had before didn't have the equalizer for videos, the latest version does have it. It makes a difference. I stayed in the car for another hour just watching the videos, because I couldn't resist splendid sound and more vivid colors LOL. Don't get me wrong, this could not compare to your TV screen, but it's just better than what I had before.

I didn't try BT yet, but WiFi connectivity is somewhat sporadic. I could not connect to my home WiFi because I was getting "Failed Configure IP" error, never seen it before. Not sure what's causing it. I was able to connect to my phone though, no problem there. Also, my big concern is that the HU doesn't seem to detect my location. I don't know if GPS functions correctly now, and which settings should be adjusted. All I know is that it worked earlier today, but not since I installed this ROM. I tried to go to Play Store, but it gave me an error "Error retrieving information from server DF-DFERH-01". I think I have to update Play Store, but I don't remember how. I'll search this forum and hopefully find a solution for that.

EDIT: For Play Store I think the problem is related to F-Droid. For me it got stuck at 29% of download. I'll have to ensure the download is complete.

Also I'd like to have a different launcher, as the minimalist style is not my style :). Hal9k mentioned there is a folder with various launchers, but I couldn't find it. I'll have to search the forum for that too.

So to recap:

1. Try multiple SD cards and USB sticks, one of them will work;

2. Try various versions of SD_Firmware_Tool to create a bootable SD card using images downloaded at different times, one of them will work;

3. If it doesn't work, try different computers to create both SD card and USB stick with ROM image.

For me it was a combination of all three above that worked. I didn't think that the choice of SD cards, USB sticks and computers would be so crucial, but apparently so. Read my previous posts for details. To get into recovery mode, I used the Power button at first, but then I would just pull the Radio fuse in the fuse box under the dashboard. It worked perfectly.

When I got into Nougat recovery mode at first, the system couldn't find the image file, it would not boot into Android 5, because it was wiped. So I got stuck with the HU with no OS. I didn't despair, and just methodically continued on copying the image on different SD cards and USB sticks (tried both methods) until I stumbled on a USB stick that worked. Don't forget to format it before copying the image. I copied just one image file to the root, no text or html files.

HUGE THANKS TO Hal9k for this excellent ROM, and to typos1 and others for their contribution and support !

I hope I will be able to fix the issues I mentioned above, or someone could point in the right direction, because I'd like to keep this ROM and would hate to roll back to Android 5.