I guess this will be different for each SBC (family) and not a generic approach. Probably something to setup within bootloader, SPI and/or u-boot. At least from our side, we don’t have such a logo implemented nor available.
I asked the “bot”. It recommended me Plymouth and, after the right questions, told me to change AUTO_SETUP_BOOT_WAIT_FOR_NETWORK=0 in Dietpi.txt and how to adjust the DietpiEnv.txt after investigating via cat /proc/cmdline, I also had to hide some loading text that was still showing.
Chose the spinner, and updated via update-initramfs -u (whatever that may be XD)