ci: Update Clang in "tidy" job

diff --git a/ci/test/00_setup_env_native_tidy.sh b/ci/test/00_setup_env_native_tidy.sh
index c14e59b7..5a2fa300 100755
--- a/ci/test/00_setup_env_native_tidy.sh
+++ b/ci/test/00_setup_env_native_tidy.sh
@@ -8,7 +8,7 @@ export LC_ALL=C.UTF-8
 
 export CI_IMAGE_NAME_TAG="mirror.gcr.io/ubuntu:24.04"
 export CONTAINER_NAME=ci_native_tidy
-export TIDY_LLVM_V="20"
+export TIDY_LLVM_V="21"
 export APT_LLVM_V="${TIDY_LLVM_V}"
 export PACKAGES="clang-${TIDY_LLVM_V} libclang-${TIDY_LLVM_V}-dev llvm-${TIDY_LLVM_V}-dev libomp-${TIDY_LLVM_V}-dev clang-tidy-${TIDY_LLVM_V} jq libevent-dev libboost-dev libzmq3-dev systemtap-sdt-dev qt6-base-dev qt6-tools-dev qt6-l10n-tools libqrencode-dev libsqlite3-dev libcapnp-dev capnproto"
 export NO_DEPENDS=1
diff --git a/src/qt/recentrequeststablemodel.h b/src/qt/recentrequeststablemodel.h
index 151f8322..7a5b71c9 100644
--- a/src/qt/recentrequeststablemodel.h
+++ b/src/qt/recentrequeststablemodel.h
@@ -18,10 +18,10 @@ class WalletModel;
 class RecentRequestEntry
 {
 public:
-    RecentRequestEntry() : nVersion(RecentRequestEntry::CURRENT_VERSION) {}
+    RecentRequestEntry() = default;
 
     static const int CURRENT_VERSION = 1;
-    int nVersion;
+    int nVersion{RecentRequestEntry::CURRENT_VERSION};
     int64_t id{0};
     QDateTime date;
     SendCoinsRecipient recipient;
diff --git a/src/qt/transactionfilterproxy.cpp b/src/qt/transactionfilterproxy.cpp
index 1ad77fd7..1f455576 100644
--- a/src/qt/transactionfilterproxy.cpp
+++ b/src/qt/transactionfilterproxy.cpp
@@ -12,9 +12,7 @@
 #include <optional>
 
 TransactionFilterProxy::TransactionFilterProxy(QObject* parent)
-    : QSortFilterProxyModel(parent),
-      m_search_string(),
-      typeFilter(ALL_TYPES)
+    : QSortFilterProxyModel(parent)
 {
 }
 
diff --git a/src/qt/transactionfilterproxy.h b/src/qt/transactionfilterproxy.h
index d0f7031a..a8570c5b 100644
--- a/src/qt/transactionfilterproxy.h
+++ b/src/qt/transactionfilterproxy.h
@@ -44,7 +44,7 @@ private:
     std::optional<QDateTime> dateFrom;
     std::optional<QDateTime> dateTo;
     QString m_search_string;
-    quint32 typeFilter;
+    quint32 typeFilter{ALL_TYPES};
     CAmount minAmount{0};
     bool showInactive{true};
 };
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index abd99fc3..57214838 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1254,8 +1254,12 @@ private:
     const CScript& scriptCode; //!< output script being consumed
     const unsigned int nIn;    //!< input index of txTo being signed
     const bool fAnyoneCanPay;  //!< whether the hashtype has the SIGHASH_ANYONECANPAY flag set
+    // Temporary workaround for a clang-tidy bug fixed in version 22.
+    // See: https://github.com/llvm/llvm-project/issues/160394.
+    // NOLINTBEGIN(modernize-use-default-member-init)
     const bool fHashSingle;    //!< whether the hashtype is SIGHASH_SINGLE
     const bool fHashNone;      //!< whether the hashtype is SIGHASH_NONE
+    // NOLINTEND(modernize-use-default-member-init)
 
 public:
     CTransactionSignatureSerializer(const T& txToIn, const CScript& scriptCodeIn, unsigned int nInIn, int nHashTypeIn) :
diff --git a/src/txdb.cpp b/src/txdb.cpp
index bb6ee2eb..93cd5948 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -38,8 +38,8 @@ namespace {
 
 struct CoinEntry {
     COutPoint* outpoint;
-    uint8_t key;
-    explicit CoinEntry(const COutPoint* ptr) : outpoint(const_cast<COutPoint*>(ptr)), key(DB_COIN)  {}
+    uint8_t key{DB_COIN};
+    explicit CoinEntry(const COutPoint* ptr) : outpoint(const_cast<COutPoint*>(ptr)) {}
 
     SERIALIZE_METHODS(CoinEntry, obj) { READWRITE(obj.key, obj.outpoint->hash, VARINT(obj.outpoint->n)); }
 };
diff --git a/src/zmq/zmqabstractnotifier.h b/src/zmq/zmqabstractnotifier.h
index 17fa7bba..47132cd5 100644
--- a/src/zmq/zmqabstractnotifier.h
+++ b/src/zmq/zmqabstractnotifier.h
@@ -21,7 +21,6 @@ class CZMQAbstractNotifier
 public:
     static const int DEFAULT_ZMQ_SNDHWM {1000};
 
-    CZMQAbstractNotifier() : outbound_message_high_water_mark(DEFAULT_ZMQ_SNDHWM) {}
     virtual ~CZMQAbstractNotifier();
 
     template <typename T>
@@ -61,7 +60,7 @@ protected:
     void* psocket{nullptr};
     std::string type;
     std::string address;
-    int outbound_message_high_water_mark; // aka SNDHWM
+    int outbound_message_high_water_mark{DEFAULT_ZMQ_SNDHWM}; // aka SNDHWM
 };
 
 #endif // BITCOIN_ZMQ_ZMQABSTRACTNOTIFIER_H