Thanks for sharing this awesome series with the community
I would try the Solidity 0.5 version of Ethernaut (https://solidity-05.ethernaut.openzeppelin.com/) (Once OpenZeppelin Contracts 3.0 is out of beta can see who in the community wants to upgrade the contracts to Solidity 0.6).
There are a number of community solutions, though it would be great if you wanted to write your own as well: Ethernaut Community Solutions
It is fairly straight forward to migrate from Truffle tests to OpenZeppelin Test Environment (and vice a versa if using mocha/chai based tests). I used this guide: https://docs.openzeppelin.com/test-environment/0.1/migrating-from-truffle
Feedback on the documentation is greatly appreciated.