As an engineer and not a researcher, are invariant subspace attacks worth digging into? Is there a better starting point than the PRINTcipher paper?
By the way, I have the feeling that these attacks are more the consequence of these sort of designs becoming more popular than any particular breakthrough in cryptanalysis. For example, the symmetry properties of the AES round were already well known long ago, but it wasn't until people started taking the AES round and building primitives out of it without adding symmetry-breaking constants that this became a problem.
[1] https://eprint.iacr.org/2015/068