The Omni20+ has a capacity of 71Wh, meaning in simple terms, you’ll get constant 71Watts for 1 hour or, say, 35.5Watts for 2 hours and so on, until you must recharge.
Peak current capacity is too small as well compared with NUC wallwart.
What do you want to gain using it, anyway?
It’s not a pure DC source, that’s for sure.
It contains switch mode regulators for its AC and DC outputs, and its AC output will not be a sinewave either.
You are probably right, intended to connect direct to DAC via USB and to avoid a costly LPS thought I could use a powerbank for dual function an travel and less cords littering the floor…
A “costly LPS” isn’t going help any anyway. The first thing the input see’s is a DC to DC converter (eg, switch mode psu) so any linear psu benefits are quickly negated. Don’t waste you money on this folly.
Roon recommend separating core and renderer functions, with good reason. I would suggest trying a raspberry pi 4 with ropieee - connected via wifi to the core, and USB to the DAC/amp.