Thank you for the explanation! Converting to a rune slice and back does give me the behavior that I wanted. It still looks butt ugly to me, but at least it works.

In Go:

    fmt.Printf("%s", string([]rune("нєℓℓσ")[1:4]))
    // єℓℓ

In Python:

    print("нєℓℓσ"[1:4])
    # єℓℓ