The wonderful thing about Matlab is that almost everything is seen as matrices or vectors, in fact this is not a disadvantage but one of its greatest strengths, therefore, a grayscale image is a 2d matrix for Matlab, a picture Color is a 3D matrix. The answer then is yes, you can use imageInputLayer to train your matrices, in fact all the procedure that occurs within deep learning in the case of images are operations with matrices.
Maybe your matrices that you want to classify are images and you have not noticed! ,
try somehow graphing your matrices and maybe your your own brain will find patterns to classify
Now in the practical case For example, if you have a 50x28 matrix :
inputlayer = imageInputLayer ([50 28], 'Name', 'entry')
or 50,28 in InputSize in the Deep Network Designer
I hope that when you see my answer in the matrix of your screen, your convolutional networks classify me as a good contributor