Just verified that I can boot the LMv2 from the usb type-c port on the back of the case.
I have an external HDD for which I found a usb3 micro b male to usb type-c male cable the debian 11 I put on there boots OK. (Writing this post from this config now).
Of course, the whole idea of the NVMe PCIe + enclosure + usb type-c was for the speed, and the HDD via USB3 is noticeably slower.