Back when specific control of the Rust version used with RIOT was needed, CARGO_CHANNEL was added to explicitly set the Rust version with consideration for CI special cases. Rust's mechansims of selecting a toolchain can be used instead now.
Closes: https://github.com/RIOT-OS/RIOT/issues/18500
Something in C2Rust mistranspiles around LED_PORT; disabling the board for all Rust examples/tests.
Unlike the hello-world example (that is largely identical), this gets run during CI.