Thank you @royk, @going, @eselarm for your time and suggestions. I really appreciate it.
I tried a lot of things, you mentioned, out of which none was working. Again, ultimately I wanted to install noble gnome, but the 25.5.1 image doesn't boot at all. So I found the older 25.2.2 noble gnome and that did indeed boot and I was able to proceed.
Interestingly this image seems to consistently detect the nvme every time. That being said, it acts very weirdly. it's extremely slow to the point that you can barely open any app, it takes a minute to change a page in settings, and sudo basically is not working (hangs indefinitely). The desktop / workspaces / app launcher are very smooth though and htop shows all 8 cores practically at idle.
Also when I boot, it first shows the splash screen (armbian loading), and then goes black indefinitely and I have to press the power button to go to the login screen (looks like it suspends after boot immediately). Poweroff doesn't work either, it hangs.
With this weird situation I was able to install the bootloader into the SPI, but I wasn't able to do an upgrade or install the full system on the nvme.
Do you have any input on this?
Some additional notes:
- All of the tests above were done with a brand new sandisk 64gb SD + balenaetcher with verify on macos.
- I've also tried Joshua Riek's 24.04 image and although it has the nvme issue, the OS runs very smoothly without any lag.
- Although the noble gnome image seems to consistently find the nvme, the minimal 25.5.1 image does not.
- My UART adapter doesn't work and a CH340 one is on it's way for boot logs.