Yes, both the T30 and T40 will boot from an NVMe SSD fitted to an adapter in the PCIe x16 slot.

You don’t need a USB stick to boot the machine or any other quirky workarounds. The BIOS / UEFI firmware will boot properly from the NVMe SSD, in a simple, cheap (£10) PCIe to m2 adapter.

Tried and tested.