Add Android Connect troubleshooting guide

docs/tip-android-connect.md

@@ -0,0 +1,24 @@
+# Tip: Android Connect troubleshooting
+
+If **Connect** closes the app or fails on Samsung / Android 12 devices:
+
+1. Install the latest **v2rayF-android-arm64.apk** from [Releases](https://github.com/drmikecrypto/v2rayF/releases).
+2. **Uninstall** older versions first (clears bad VPN/core state).
+3. Use a **Compat** VLESS link — avoid `flow=xtls-rprx-vision` on phones.
+4. Tap **Connect** and allow the **VPN** permission when prompted.
+5. If connect fails, read the status message — the app tears down VPN so normal internet keeps working.
+
+## Still broken?
+
+With USB debugging enabled:
+
+```bash
+adb logcat -s v2rayF
+```
+
+Tap Connect and check for `XRAY_TUN_FD`, `libxray.so`, or VPN errors.
+
+## Technical notes (v1.1.8+)
+
+- Xray on Android reads the VPN TUN fd from the `XRAY_TUN_FD` environment variable.
+- The core runs from `libxray.so` in native libs with `LD_LIBRARY_PATH` set at launch.