The SNAPSHOT branch recommended in the WIKI for initial installation when upgrading from the original firmware doesn't work. It can't be flashed using the recommended commands. Also, when booting via UART, the *-initramfs-recovery.itb recovery file from the TFTP protocol (192.168.1.254) doesn't load.
The file of the same name works fine from the ImmortalWrt branch.
The *-nand-preloader.bin file also doesn't load, not on any router version. DDR3, DDR4, NAND, EMMC are supported. But since it works without it, you can mark it as unimportant in the firmware manual.
Also, the division of these files into DDR3 and DDR4 files in the SNAPSHOT branch, unlike in the 24.10.4 branch, is considered harmful. This is because there is no 100% accurate algorithm for determining the type of installed memory. The model codes described in the WIKI are not an exact indication of the memory type. Two routers were damaged, both with NAND and EMMC memory.
I hope this information is helpful.
You have UART access, you claim 'it doesn't work', however no logs to back it up, which means no hints to fix it either.
You misunderstood. I simply stated the fact that it doesn't work. I don't need recommendations. As I wrote above, I solved it by flashing a file from the ImmortalWrt project. It works, which suits me perfectly. This is for informational purposes only. The routers have been flashed and are already in use. Regarding the logs, when flashing the stock firmware, it says it can't open the file, which is exactly the same as when trying to flash *-rax3000m-nand-ddr4(3)-preloader.bin. When booting via UART, there's simply an empty log after the file has successfully loaded into memory. In other words, no messages at all. It should indicate which file is loading or waiting to load, but there's nothing.
Your workaround is not a solution, even if it works for you. If you want to contribute to a solution, a bug report (and logs of the failure, beyond 'doesn't work'!) is essential (it's not a guarantee that it will be fixed, but required to realize what's broken so it may be fixed). If you don't want it to be solved that's fine as well, just don't complain that it won't 'ever' be fixed then.