Thanks for the advise, but the links you provided are not going to help much. I need to use RTL8812AU dongle in broadcast mode (as in OpenHD, see https://openhd.gitbook.io/open-hd/hardware/wifi-adapters), so I need to connect to USB port, not SD card slot.
And I don't need the CSI camera at all ...

I'd like to use Pico as a router between a PC connected through USB WiFi dongle, security cameras DVR connected through Ethernet, and a controller connected through UART. What's the easiest way to do that? Is there a ready to use firmware for it?