If you're just using a standard RTL-SDR, then yes, an upconverter like HamItUp or SpyVerter would work.

However, the LimeSDR Mini supports down to 10MHz out of the box, which is "good enough".

If you really need to get the 160, 80, 60, and 40 Meter bands then the converter would be needed, or you can just use the previous-generation the (full size) LimeSDR, which can receive down to 100KHz.