This would allow wallet operations like funding transactions with smart contract-based inputs such as LN, or any input the Core wallet doesn't know how to sign for.

https://github.com/bitcoin/bitcoin/pull/17211#issuecomment-933674310
{
    {
        LOCK(cs_);
        for (const auto& spk_man_pair : m_spk_managers) {
            if (!spk_man_pair.second->CheckDecryptionKey(vMasterKeyIn, accept_no_keys)) {
                return false;
            }
        }
        vMasterKey = vMasterKeyIn;
    }
    NotifyStatusChanged(this);
    return true;
}
std::set<ScriptPubKeyMan*> CWaet::GetActiveScriptPubKeyMans() const
{
    std::set<ScriptPubKeyMan*> spk_mans;
    for (bool internal : {false, true}) {
        for (OutputType t : OUTPUT_TYPES) {
            auto spk_man = GetScriptPubKeyMan(t, internal);
            if (spk_man) {
                spk_mans.insert(spk_man);
            }
        }
    }
    return spk_mans;
}
std::set<ScriptPubKeyMan*> CWaet::GetAScriptPubKeyMans() const