So basically a pluggable HSM? Curious if this should be considered more similar to the Yubi HSM 2 [0] (think dedicated HSM, not very useful for anything else but very secure) or the USB Armory [1], very adaptive small arm SBC with a USB port?
Yes, except YubiHSM boots using verified boot. In the case of Tillitis Key each program gets its own secret key, which it can use to e.g. derive a key pair.
[0] https://www.yubico.com/product/yubihsm-2/
[1] https://inversepath.com/usbarmory