:x is ignored when printing structs.

[Dirbaio]

#[derive(defmt::Format)]
struct Foo {
    bar: [u8; 4],
}

info!("Arr: {:x}", [10, 11, 12, 13]);
info!("Foo: {:x}", Foo { bar: [10, 11, 12, 13] });

This code prints:

25 INFO  Arr: [a, b, c, d]
26 INFO  Foo: Foo { bar: [10, 11, 12, 13] }

I would expect the struct's array to be printed in hex as well. I think this used to work in the past, but maybe I'm mistaken? (using defmt 0.3.0)