> I run two monitors off my M1 mbp - works for me

Lucky you. It works horribly for me - any time the screen is locked (corporate policy locks it after a certain period of inactivity) the OS forgets all about the external screens.

When I unlock the machine, all my windows are on the internal screen.

There's a setting somewhere along the lines of "each display is an individual workspace" that "fixes" the issue by making each screen an independent workspace, which still won't remember where the windows are.

Record your preferred screen config using displayplacer [1] and then run that via a shortcut.

[1]: https://github.com/jakehilborn/displayplacer