> i1 : ZZ/2[t]; i2 : isPrime(t^2+t+1) uniivariate factorization not implemented 
>>this is caused by undetected NTL by 
>>factory. Should we patch factory in a way that NTL is mandatory?

> I'm hesitant to patch,

then we could patch Singular directly (at least improve the error message):
https://github.com/Singular/Sources/pull/530

Now I also recall that we can't define NTL mandatory without restricting the M2 licensing model.