I'm having great success with Eagle 9.2.2. I make small boards for through-hole components and, so far have been able to get everything on a single layer without jumpers but next project will require them.
I do an outline on the Milling layer and the router4 cuts out the board.
I have NOT been able to get a 1/4 inch hole recognized and cut however. It doesn't get picked up by PCB-GCODE and doesn't get cut. I use the Circle command in Draw to make the hole. I've put it on the milling layer and alternatively on the Dimensions layer, but no-joy.
It possible that I don't have Eagle set up right?
What would you look at if this was your problem?