Since #13666 our fee calculation assumes that ECSDA signatures are a maximum of 71 bytes, rather than 72. However, not all hardware wallets implement R-value grinding.

This can cause us to underpay fees when using an external signer. That's especially problematic when the user picks 1 sat/vbyte as the fee, because it won't even get into our own mempool.

The easiest solution would be to modify `ExternalSignerScriptPubKeyMan` to assume 72 bytes for ECSDA signatures.

Slightly more advanced would be to expand HWI to keep track of which devices and firmware versions (if any) support R-value grinding. We'd then have to store that in the wallet in some new field. Personally I'd rather work on better Taproot support, which thanks to Schnorr avoids this issue altogether. 
std::optional<CAmount> GetEffectiveTotalAmount() {return total_effective_amount; }
private:
    
    CAmount total_amount{0};
    
    std::optional<CAmount> total_effective_amount{0};
};
struct CoinFilterParams {
    
    CAmount min_amount{1};
    
    CAmount max_amount{MAX_MONEY};
    
    CAmount min_sum_amount{MAX_MONEY};
    
    uint64_t max_count{0};
    
    bool only_spendable{true};
    
    bool include_immature_coinbase{false};
    
    bool skip_locked{true};
};
/**
 * Populate the CoinsResult struct with vectors of available COutputs, organized by OutputType.
 */
CoinsResult AvailableCoins(const CWallet& wallet,
                           const CCoinControl* coinControl = nullptr,
                           std::optional<CFeeRate> feerate = std::nullopt,