I'm looking for a list of tools similar to ATAT which are available for creating random multi-component alloy inputs for DFT/MD.
There are a number of open-source and commercial software that can do a completely random substitution alloy.
In the open-source segment, you can try the python software: Pymatgen (https://pymatgen.org/). Atomsk (https://atomsk.univ-lille.fr/) is another great software to do this. I have tried to do this using Atomsk and it works perfectly.
In the commercial software segment, you can try the model builder routine of QuantumATK (https://www.synopsys.com/silicon/quantumatk.html).