The paper is available on the IACR ePrint Archive.
You can find the code to prepare the internal state (Section 4.2) in
linearized_ascon/experiment_initial_conditions.py
You can find the code to find a random-prefix-preimage based on a prepared internal state (Section 4.3) in
linearized_ascon/experiment_more_solutions.py(Python version)fast_linearized_ascon(optimized C++ version)