Hi, I just received my Alta and tried powering it up for the first time today as well.
For reference, the label printed on my board is AML-A311D-CC-V1.0C.
The first time I powered it on, I tried it with no SD card (or EMMC card) attached, just to see what it would display on the debug port. The messages displayed looked pretty much like what you are showing above.
Next, I flashed an SD card with the latest Raspian release from Libre’s Distro Server (2023-10-10-raspbian-bookworm-arm64-full+arm64.img.xz, dated 2023-Dec-03). I inserted the SD card in the Alta and powered it up (I noticed that the SD slot is not spring-loaded - you just push the card in and there is no latch or anything - this is not like the Le Potato or Sweet Potato boards). It powered up and I was able to get to the desktop.
I was able to reboot by issuing a sudo reboot command from the terminal, or by selecting “Logout” and “Reboot” from the Rasberry Pi Menu in the Desktop. I rebooted a couple of times without issue.
However, my Ethernet also appears a little flaky…
The first time I booted (even without an SD card), the DHCP service was able to get an IP address from my router. I could see it connected in the Router’s admin screen. I assigned it a reserved IP address in the router and the board updated to use the new address. But, after I tested the re-boot sequence a couple of times and was in the Raspian desktop, I noticed that it kept popping up messages about the network being unavailable. ifconfig did not show any IP address at all.
Doing a full shutdown and completely removing power from the board, then restarting seemed to have fixed the Ethernet, but I will have to keep an eye on it.
Anyway, you may want to verify that you have the latest version of the SPI flash firmware installed. These can be found here: https://boot.libre.computer/ci/.
As of today, the latest firmware is dated Dec 14, 2023. Surprisingly, it appeared that mine was already up to date. Maybe yours is not?
See this post for details: https://hub.libre.computer/t/libre-computer-board-bios-firmware-update-images/3113.
If that doesn’t do it, you might want to give the Raspian OS a try. Your symptoms don’t sound like an operating system problem to me, but I’m no expert.
-Good Luck!