how do i flip my m1 to portrait display

In display settings, there should be an Orientation option. Change landscape to portrait. Note that this will not work on MacBooks unless you are connected to an external display.

this article explains what you need to know:

https://appleinsider.com/articles/21/05/30/how-to-rotate-your-monitor-and-use-it-vertically-in-macos

As already noted, this does not work for the laptop internal display. That used to be possible in older versions but not in Monterey, but I am sure it has disappeared somewhat before, maybe in Mojave or High Sierra.

I am not aware of any third party tool for this, but look up those applications that offer extra display resolutions, maybe one of them supports this feature.

Like an iPad? Not possible.