DisplayLink. The Dell box I use to hotdesk my office laptop by day also works as a KVM on my pixel 9a. I get power, monitor, keyboard, mouse and ethernet on one cable.
As far as i know, display link requires software not available on the pixel, so you must be using display port and confusing both. Display port supports all the things you said
No. DisplayLink is video out over a regular USB connection, not “alt mode”. It’s for when you don’t have true video out. It’s compressed to hell and stupid.