It's not clear to me if dropping support for this functionality was intentional.

Chain of events:

- #21689 removed test coverage due to a misunderstanding due, I believe, to this functionality being generally supported by all platforms except macOS which does not and returns a different format
- #21756 removed support and caused this regression
- #21690 restores the test coverage that would have caught this regression

Currently, neither the test coverage before #21689 nor the coverage restored by #21690 pass since the merge of #21756.

{
    return IsIPv6() &&
           HasPrefix(m_addr, std::array<uint8_t, 12>{0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                     0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00});
}
bool CNetAddr::IsRFC4843() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 3>{0x20, 0x01, 0x00}) &&
           (m_addr[3] & 0xF0) == 0x10;
}
bool CNetAddr::IsRFC7343() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 3>{0x20, 0x01, 0x00}) &&
           (m_addr[3] & 0xF0) == 0x20;
}
bool CNetAddr::IsHeNet() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 4>{0x20, 0x01, 0x04, 0x70});
}
/**
 * Check whether this object represents a TOR address.
 * @see CNetAddr::SetSpecial(const std::string &)
 */
bool CNetAddr::IsTor() const { return m_net == NET_ONION; }
/**
 * Check whether this object represents an I2P address.
 */
bool CNetAddr::IsI2P() const { return m_net == NET_I2P; }