Not one but two cool pure bare metal examples were recently posted to the forums.

First for the Raspberry Pi Pico... "Zero lines of C. Not even the vector table, boot2, or startup code. The only non-Swift file is the linker script."

https://forums.swift.org/t/bare-metal-raspberry-pi-pico-examples-written-entirely-in-swift-no-c-code-at-all/85454