Many SBCs will boot from NVMe via USB. Check out Armbian's tool armbian-install https://docs.armbian.com/User-Guide_Getting-Started/#how-to-install-to-emmc-sata-nvme-usb. There's too many SBCs to list that are capable. Also keep in mind the power to run an SSD and what power your USB connection has available. You may need to use a powered hub. If you have a budget in mind that would help to narrow down your choices.