The "Unitary Patterns" kata offers tasks on creating unitary transformations which can be represented with matrices of certain shapes (with certain pattern of zero and non-zero values).
You can run the Unitary Patterns kata as a Jupyter Notebook!
A lot of tasks of this kata have been featured in the Microsoft Q# Coding Contest - Winter 2019. You can find the descriptions of their solutions in the editorials for the warmup round and for the main contest.