Basically, I want to know if one scanner can record multiple channels
simultaneously.

Ninety percent of the time a scanner is a single receiver that
sequentially selects a single programmed frequency, one at a time. You
would need multiple scanners, or a ham rig that can scan with built in
multiple receivers like the Yaesu FT-8900R or an old triband Kenwood
742D, but it would not do trunking. That Kenwood model has a mode for
separate speaker outputs for each receiver. The Yaesu dumps both
receivers to a single speaker.