I'm using the reversible trunk liner that came with my Santa Fe (from Hyundai), using the rugged side (non-carpeted). The SmartLiner set I bought for the 2021 was just front and second row. The Hyundai trunk liner is relatively flexible and still gives access to the under-storage. It doesn't provide a deep bucket like I had in my 2004, but good enough for now. I may get their 2019-2021 trunk mat eventually if reviews suggest it really is compatible with the 2021, but I'd expect it to make the under storage more difficult.

I just got a 2021 Santa Fe Limited. It came with no floormats, which surprised me. After some reading I ordered the 2021 Santa Fe version. Do you (still) like yours? Worst case I can return them and get Weathertech at quite a bit more, but currently Weathertech only offers the front mats for the 2021 Santa Fe.