Rock3b with power bank

Hi,
I would like to use rock 3A or rock 5B as a smart home hub. I don’t want for thr smart home to stop working if there is an electricity outage. I’m thinking for simple UPS solution for the SBC. Will a simple 20000mah power bank with USB PD work as UPS? Power rock board from the power bank and have power bank permanently connected to the electricity grid is it viable option ? Am I too naive ?

It is difficult to find a power bank that can output power while charging at the same time.

I pnly knows that there are many lithium battery backup power pcbs on Taobao.

If you can find something like that, choose one with output voltage of 12V and current greater than 3A, 12v power supply can be directly connected to typec port on 3a/5b, but you must be very carfully of the polarity.