I suspect most people will initially hit here as I am the author of Auctionmaid Matrixrate, which is the original multiple tablerates via csv file extension.
I’m also seeing people struggling with getting up and running with Magento, so I’m going to put some of my musings on here. The Magento forum is great for getting answers, but I find it’s all very chaotic, so hopefully I can make sense of some of it. You never know!