Why - in that example with an extended lambda - is an ambigious copy constructor and some deleted function

Question

I do not understand the behaviour of the following code:

template< bool b >
struct Foo {
  Foo() = default;
  __host__   Foo( const Foo & ) requires(  b ) {}
  __device__ Foo( const Foo & ) requires( !b ) {}  
};

template< typename Lambda >
__global__
void kernel( Lambda ) {}

int main() {
  Foo< true > foo;
  auto la = [foo] __device__ (){ };
  kernel<<< 1, 1 >>>( la );
}

When I compile it with nvcc 12.1 and gcc 11.3 as host compiler (nvcc main.cu -std=c++20 --expt-extended-lambda) I get two errors

• copy constructor for class "Foo<true>" is ambiguous
      auto la = [foo] __attribute__((device)) (){ };
                 ^
  

• function "lambda []()->void::<unnamed>(const lambda []()->void &)"
  (declared implicitly) cannot be referenced -- it is a deleted function
      kernel<<< 1, 1 >>>( la );
                          ^
  

I do not understand both errors.

• Why is the copy ctor ambigious?
• Which function is deleted at all and at what place wanted the compiler use it?