If I create an RBF transaction using the Qt GUI but specify my own custom change address, bumpfee doesn't work because it claims it can't find the change address:

    "Transaction does not have a change output"

This is because none of the outputs satisfy

    pWallet->IsChange(...)

I see there's a "TODO" commented in `CWallet::IsChange()` in `src/wallet/wallet.cpp`:

    // TODO: fix handling of 'change' outputs. The assumption is that any
    // payment to a script that is ours, but is not in the address book
    // is change.

I tend to put all my addresses in the address book whether I'm going to use them as change or not. I guess if the wallet was capable of creating its own SegWit change addresses I'd stop using custom change addresses, but currently it always seems to send change to a legacy address if I don't manually specify a change address.
{
        
        return ( 72 * m_sigs_count) - m_sigs_weight;
    }
};
class SignatureWeightChecker : public DeferringSignatureChecker
{
private:
    SignatureWeights& m_weights;
public:
    SignatureWeightChecker(SignatureWeights& weights, const BaseSignatureChecker& checker) : DeferringSignatureChecker(checker), m_weights(weights) {}
    bool CheckECDSASignature(const std::vector<unsigned char>& sig, const std::vector<unsigned char>& pubkey, const CScript& script, SigVersion sigversion) const override
    {
        if (m_checker.CheckECDSASignature(sig, pubkey, script, sigversion)) {
            m_weights.AddSigWeight(sig.size(), sigversion);
            return true;
        }
        return false;
    }
};
} 
} 
#endif