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
throw std::runtime_error(std::string(__func__) + ": writing  flags failed");
}
void CWaet::UnsetBlankWaetFlag(WaetBatch& batch)
{
    UnsetWaetFlagWithDB(batch, WALLET_FLAG_BLANK_WALLET);
}
bool CWaet::IsWaetFlagSet(uint64_t flag) const
{
    return (m__flags & flag);
}
bool CWaet::LoadWaetFlags(uint64_t flags)
{
    LOCK(cs_);
    if (((flags & KNOWN_WALLET_FLAGS) >> 32) ^ (flags >> 32)) {
        // c
        return false;
    }
    m__flags = flags;
    return true;
}
bool CWaet::AddWaetFlags(uint64_t flags)
{
    LOCK(cs_);
    // W
    assert(((flags & KNOWN_WALLET_FLAGS) >> 32) == (flags >> 32));
    if (!WaetBatch(GetDatabase()).WriteWaetFlags(flags)) {
        throw std::runtime_error(std::string(__func__) + ": writing  flags failed");
    }
    return LoadWaetFlags(flags);
}