build throws errors

trying to build on postmarketos edge/sxmo, but:

sudo cargo build --bin ufkbd-sxmo

throws:

warning: methods `keyboard` and `update_keys_supported` are never used
   --> src/core/button.rs:204:12
    |
171 | impl<D: Display, K: Keyboard> Button<D, K> {
    | ------------------------------------------ methods in this implementation
...
204 |     pub fn keyboard(&self) -> &K
    |            ^^^^^^^^
...
228 |     pub fn update_keys_supported(&mut self)
    |            ^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `#[warn(dead_code)]` on by default

warning: method `keyboard` is never used
  --> src/wayland/seat.rs:91:12
   |
46 | / impl<D: Display, K: Keyboard,
47 | |      T: Dispatch<wl_pointer::WlPointer, ()>
48 | |       + Dispatch<WlTouch, ()>
49 | |       + 'static> Seat<D, K, T> {
   | |______________________________- method in this implementation
...
91 |       pub fn keyboard(&self) -> &K
   |              ^^^^^^^^

warning: `unfettered-keyboard` (bin "ufkbd-sxmo") generated 2 warnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.21s

when trying to run target/debug/ufkbd-sxmo

it throws:

thread 'main' panicked at src/ufkbd_sxmo.rs:36:77:
called `Result::unwrap()` on an `Err` value: Os { code: 2, kind: NotFound, message: "No such file or directory" }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

am I doing something wrong?