Didn’t like the tone of my last attempt to reply, so here’s a rundown from a hardware enthusiast perspective.
Single board computers with no thunderbolt cannot have an external GPU, and have soldered permanent processors
The U sku on that cpu denotes low voltage. That cpu will have much worse performance than you expect. Ghz numbers usually advertise boost clocks, not stable performance.
Even when an external GPU is an option, the memory bandwidth of thunderbolt is not sufficient to run most cards and will result in micro stuttering and overall reduced performance. Usually you lose ~30%-50% of your performance depending on the card.
To top all of this off, you cannot use the steam deck as a reasonable expectation for this class of hardware. The deck runs a custom APU with a beefier than normal GPU. You will not get that performance from the linked micro pc.