I use from 1 year dietpi (now with 8.22.3 version) on my Odroid n2+ (unattended server) without any problem: until now I only used eMMC card (32GB) but recently I buyed a DAS module (Sabrent DS-SC5B) and I attached it to Odroid via USB 3.0 (actually with only 1 SATA disk).
I mounted this disk with dietpi-drive_manager and works perfectly: but when I reboot (with USB cable attached to Odroid) Dietpi doesn’t boot.
So it even doesn’t try to boot until it’s disconncted sounds like a hardware issue to me? Or a power issue. But the Sabrent DS-SC5B has it’s own power brick.
Do you use a metal case for the N2 by any chance?
Usually the boot process needs there most power, when everything is starting up, a lot of reads and writes taking place, the network gets in initialized and so on. Usually this is the part where poor power connection fails the most.
But the thing is, it would even try to boot but even this does not happen with something to USB attached which makes me think that a plugged in USB device is shortening something on the board? But on the other hand you can boot from an USB Stick, which suggests the sabrent is the main culprit and not the USB port.
Can you try to connect another HDD via USB an observer what happens? Or try another cable with the sabrent ?