Fixed the same thing for 1.21.5

versions/1.21.5/src/main/java/org/saturnclient/impl/mixins/MinecraftClientMixin.java

@@ -127,4 +127,36 @@ public abstract class MinecraftClientMixin implements MinecraftClientRef {
     public void executeOnThread(Runnable runnable) {
         ((java.util.concurrent.Executor) (Object) this).execute(runnable);
     }
+
+    @Override
+    @SuppressWarnings("resource")
+    public String getPlayerListEntry(UUID uuid) {
+        var client = (MinecraftClient) (Object) this;
+        var handler = client.getNetworkHandler();
+
+        if (handler == null)
+            return null;
+
+        var entry = handler.getPlayerListEntry(uuid);
+        if (entry == null)
+            return null;
+
+        return entry.getProfile().getName();
+    }
+
+    @Override
+    @SuppressWarnings("resource")
+    public UUID getPlayerListEntryUUID(String name) {
+        var client = (MinecraftClient) (Object) this;
+        var handler = client.getNetworkHandler();
+
+        if (handler == null)
+            return null;
+
+        var entry = handler.getPlayerListEntry(name);
+        if (entry == null)
+            return null;
+
+        return entry.getProfile().getId();
+    }
 }

versions/1.21.5/src/main/java/org/saturnclient/saturnclient/PlayerTracker.java

@@ -1,52 +0,0 @@
-package org.saturnclient.saturnclient;
-
-import net.fabricmc.fabric.api.client.networking.v1.ClientPlayConnectionEvents;
-import net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents;
-
-import org.saturnclient.client.ServiceClient;
-
-import net.minecraft.client.network.PlayerListEntry;
-import net.minecraft.client.MinecraftClient;
-
-import java.util.HashSet;
-import java.util.Set;
-import java.util.UUID;
-
-import com.mojang.authlib.GameProfile;
-
-public class PlayerTracker {
-    private static Set<UUID> trackedPlayers = new HashSet<>();
-
-    public static void initialize() {
-        // When client joins a server, reset tracked players
-        ClientPlayConnectionEvents.JOIN.register((handler, sender, client) -> {
-            trackedPlayers.clear();
-            client.execute(() -> {
-                checkForNewPlayers(SaturnClient.client);
-            });
-        });
-
-        // Check for new players every tick
-        ClientTickEvents.END_CLIENT_TICK.register(client -> checkForNewPlayers(client));
-    }
-
-    private static void checkForNewPlayers(MinecraftClient client) {
-        if (client.getNetworkHandler() == null)
-            return;
-
-        for (PlayerListEntry player : client.getNetworkHandler().getPlayerList()) {
-            UUID playerUUID = player.getProfile().getId();
-
-            if (!trackedPlayers.contains(playerUUID)) {
-                // A new player has joined
-                onPlayerJoin(client, player);
-                trackedPlayers.add(playerUUID);
-            }
-        }
-    }
-
-    private static void onPlayerJoin(MinecraftClient client, PlayerListEntry player) {
-        GameProfile profile = player.getProfile();
-        ServiceClient.player(profile.getId(), profile.getName());
-    }
-}