Macbook Air M1 2020 - Can have two external monitors with different displays

I have a thunderbolt dock: hp thunderbolt dock 280w g4.

I have two monitors (hp e223 and sceptre m25) on displayport cables going into the dock. (HDMI seemed to flicker even with one monitor--and it flickered with both hp and sceptre.)

I have the thunderbolt cable going out from the dock into the macbook air.

Both monitors show the desktop extended from the built in display, but both external monitors are mirrors of each other and show the same content.

Only the HP shows up in displays in settings. Detect displays does not help.

There are several usb C ports on the dock-- usc ss and thunderbolt. I tried connect the extra port on the macbook to each of those but that did not change anything.

My mac specifications (MacBook Air (M1, 2020) - Technical Specifications) seem to say that I can only have one external, but are little vague as to whether I can do more at lower resolution, and I thought I heard it was possible?

Do I need a monitor with a usb c output or is it just not happening?

Thanks.