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.

{
    std::string suffix;
    switch (network.m_net) {
    case NET_IPV4:
    case NET_IPV6: {
        assert(network.m_addr.size() <= sizeof(netmask));
        uint8_t cidr = 0;
        for (size_t i = 0; i < network.m_addr.size(); ++i) {
            if (netmask[i] == 0x00) {
                break;
            }
            cidr += NetmaskBits(netmask[i]);
        }
        suffix = strprintf("/%u", cidr);
        break;
    }
    case NET_ONION:
    case NET_I2P:
    case NET_CJDNS:
    case NET_INTERNAL:
    case NET_UNROUTABLE:
    case NET_MAX:
        break;
    }
    return network.ToString() + suffix;
}
bool CSubNet::IsValid() const