I have created the file gerber for my PCB to realize perhaps in NextPCB.
I have sent the file gerber but the supplier said that the outline layer file gerber is missing.
In the annexed screenshot you can see what I have selected.
For the edges of the PCB you have to draw lines on the Edge.Cuts layer:
They are normal graphic lines and arcs from the Pcbnew / Place / Line menu. Do not use Polygons on Edge.Cuts.
It is important to realize that the line and arc segments mus form a closed shape. The easiest way to do this is to use a coarse grid (For example whole millimeters). You can also snap line segments to each other by dragging a line endpoint to another line endpoint. When a snap point is recognized, an additional small circle is drawn around the crosshair mouse pointer.
I have realized the line around the PCB using “add graphic lines” and Edge.Cuts was selected, but when I have generated the files gerber I didn’t obtain the “outline layer file gerber”