add note for ubuntu and openeuler

Author: qyh111

docs/source/getting-started/quickstart_vllm_ascend.md

@@ -41,6 +41,14 @@ Download the pre-built `vllm-ascend` docker image and build unified-cache-manage
  cd unified-cache-management
  docker build -t ucm-vllm:latest -f ./docker/Dockerfile-NPU ./
  ```
+vllm-ascend provides two variants: **Ubuntu** and **openEuler**.  
+The `Dockerfile-NPU` uses the **openEuler** variant by default.
+
+If you want to use the **Ubuntu** variant, please remove the `-openeuler` suffix and use the following image instead:
+
+```text
+quay.io/ascend/vllm-ascend:v0.9.2rc1
+```
 Then run your container using following command. You can add or remove Docker parameters as needed.
 ```bash
 # Update DEVICE according to your device (/dev/davinci[0-7])