Recently, while moving and getting some furniture from IKEA, I found the perfect frame to host the RGB matrix, the RIBBA frame:

The matrix is 190.5mm x 190.5mm x 14mm, the frame is 230mm x 230mm x 45mm, plenty of space for the matrix and the electronics. The frame has a white cardboard insert that can be cut to the matrix size:

However the matrix will not be centred...

So I 3D printed some corners to center the matrix in the frame and push it against the front face:

The electronics are not looking very professional though, I need to rethink that, wires are pretty unreliable...