AdvancedParaEQ: use slot 1 as a multi-slot-capable canary

G522 advertises 6 RO + 10 custom slots in getEQInfos but the firmware
only honors slot 0; LGHUB never touches the rest either. Probing all 16
generated 15 NOT_SUPPORTED log lines per device boot. Probe slot 0,
then slot 1 as a canary — if it fails, skip the remaining 14 redundant
probes. Behavior is unchanged on hypothetical multi-slot firmware:
slot 1 success triggers the full 0..total-1 probe.

lib/logitech_receiver/advanced_para_eq.py

@@ -330,11 +330,11 @@ def probe_advanced_eq_slots(device, direction=DIRECTION_PLAYBACK, info=None):
     total = ro_count + custom_count
     if total == 0:
         return []
-    working = []
-    for slot in range(total):
+
+    def probe(slot):
         bands = get_advanced_eq_params(device, direction=direction, slot=slot)
         if bands is None:
-            continue
+            return None
         name = get_advanced_eq_friendly_name(device, direction=direction, slot=slot)
         kind = "factory" if slot < ro_count else "custom"
         logger.info(
@@ -345,7 +345,33 @@ def probe_advanced_eq_slots(device, direction=DIRECTION_PLAYBACK, info=None):
             name,
             [f"{_band_label(t, f)} {round(g, 2)}dB" for t, f, g in bands],
         )
-        working.append((slot, name, bands))
+        return (slot, name, bands)
+
+    working = []
+    # Slot 0 is canonical. If it fails the device is unusable; bail.
+    entry = probe(0)
+    if entry is None:
+        device._advanced_eq_working_slots = working
+        return working
+    working.append(entry)
+    # Slot 1 acts as a "multi-slot capable?" canary. G522 firmware
+    # advertises 16 slots but only honors slot 0; LGHUB itself never
+    # touches slots > 0 on this device. When the canary fails, skip the
+    # remaining 14 NOT_SUPPORTED probes.
+    if total > 1:
+        entry = probe(1)
+        if entry is None:
+            logger.info(
+                "AdvancedParaEQ: slot 1 returned NOT_SUPPORTED; " "firmware advertises %d slots but only honors slot 0",
+                total,
+            )
+            device._advanced_eq_working_slots = working
+            return working
+        working.append(entry)
+        for slot in range(2, total):
+            entry = probe(slot)
+            if entry is not None:
+                working.append(entry)
     device._advanced_eq_working_slots = working
     logger.info(
         "AdvancedParaEQ working slots on dir=%d: %d of %d advertised %s",