Pixel 8a works just fine.

It's still using mirror mode by default. There's a Desktop mode you can enable in developer settings which works well with the NexDock hardware, but the desktop mode UI is still pretty buggy at the moment.

Google only recently enabled USB-C display mode recently. It is only the Pixel 8 and later. Don't know if earlier phones will get it, it depends on having the hardware and getting the OS update.