I understand what undefined behavior is, I just don't dereference pointers or optionals without first checking them against nullptr or nullopt (respectively). In fact, I generally use the .has_value() and .value() interface on the optional which, to my point in the above comment, is a very similar workflow to using an optional in Rust.

I think if you adopted a more defensive programming style where you check your values before dereferencing them, handle all your error cases, you might find C++ is not so scary. I would also recommend not using auto as it makes the types less clear.

    std::optional<int> v = std::nullopt;
    if (v == std::nullopt) {
        return std::unexpected("Optional is empty.");
    }

    std::println("{}", *v);

If you are dereferencing things without checking that they can be dereferenced I don't know what to tell you.