I forgot how frustrating Blender’s boolean modifiers can be sometimes. I did try but Blender crashed my computer.

I’m about ready to give up on solving this problem that i have no personal stake in, but here’s what i was planning to do.

1. Open a blank keycap model in Blender and import that SVG.
2. Convert all the line segments to meshes and join them into a single object.
3. In edit mode, extrude Tux to make him 3D.
4. In object mode, line him up with the top (or front, i guess) of a key and shrink and rotate him so he sticks into the cap.
5. Select the key and make a boolean difference modifier on it with Tux. This should cut a Tux-shaped hole into the cap.
6. Export as STL and import into a slicer program for 3D printing.

I found suitable caps for MX and Choc V1, though i didn’t get around to trying the Choc files.

The SVG i used is based on the flat one here, and my monochome single-object version is here, since i can’t upload an SVG in a comment here. It’s text but you can copy that into a plain text editor (xed, Notepad, etc.) and save it as an SVG file.

On the custom keyboard i’m designing, my plan is actually to use U+2756 ❖ as the legend for my super key if i ever put legends on the keys. That key doesn’t have a standard symbol but this one works well enough.