Ikosaeder Eckteil

Please see https://www.thingiverse.com/thing:1862570 for the remaining parts, 20 equilateral triangles are needed to form a globe. Not included here.

Recreated the icosahedron_insert_v04 with FreeCAD using only the Part workbench.
The STL of version v04 seems to have a face inclination angle of 52.0° which results in 59.5° corners of the triangles. For correct 60° triangles we use 52.623° inclination here.

The holes are replaced by pockets for neodym magnets of 8mm diameter, 2mm high.

There are two versions of the pieces, one (_cyl) has a cylindrial pocket for connecting magnet, centering it precisely. Not sure if that precision is helpful. In cas it is not, there is a second (_tri) version, that has a large triangular cutout, giving the connecting piece more freedom.

For both, there is a positioning aid included, that help gluing the touching magnet on the right spot.

The FreeCAD source is included to allow parametric modifications.