Can no longer shrink left and right panels much?

If you used the Apple Migration Assistant, the LR preferences got transferred, and it's possible that LR is now getting confused by stale sizes recorded in the preferences.  Try resetting LR's preferences:
https://www.lightroomqueen.com/articles-page/how-do-i-reset-lightrooms-preferences/

LR sometimes soils its preferences file, and resetting it can fix all sorts of wonky behavior. That article explains how to restore the old preferences if resetting doesn't help.

Is there a difference in the height and width of the screen, in pixels, between the Intel and M2 Mac? Or in the Display settings? If the M2 Mac is uses different display settings, you could have less or more screen space.

If you are able to set the new Mac to the same UI resolution as the old Mac, you can have the same spacing as you did on the old Mac.

For example, My M1 MacBook Pro defaults to a UI resolution of 1512 by 982 pixels. This is less than the 2560 by 1440 pixels of my big desktop Mac display, so applications seem more crowded on the laptop. I wanted the MacBook work area to be closer to my Mac desktop, so in Displays I clicked More Space. That results in a UI resolution of 1800 by 1169 pixels, which shrinks everything to give the image preview more room between the panel stacks in Lightroom Classic.

It looks to me from the spacing of the tools below the histogram that the side bars are at minimum size.  What is the size of your screen and do you have it set to default resolution or did you lower the resolution?  

You should be able to hover your mouse at the boundary between the panels and the image, it will turn into a double-sided arrow and then you can drag to the left or right to change the size of the panels.