Is there a syntax to specify multiline code snippets in Google (Hangouts) Chat?

I would like something like the Markdown options (of SO?), where

four leading spaces makes it look like code
blocks have been written

Google (Hangouts) Chat only supports basic (not rich nor full Markdown) formatting. For your specific inquiry, use pairs of triple backticks, i.e.,

```
Hello
World
```

For this and other formatting directives, see either the consumer help page (for end-users), or the format messages page (for developers) in Google's documentation.

For those who are developers and want to build Google Chat apps/bots, I was part of the launch team back in 2018 and produced some video content to help you get started:

• Take a look at the developer intro and Google I/O launch videos. The intro shows you how to build (synchronous) bots that respond in real-time to user requests with an @BOT message.
• You can also write bots/apps that send alerts or notifications in an asynchronous manner. For information on how to do that, check out the 2nd developers video.

Ensure you're either pasting plaintext or force plaintext with cmd/ctrl + shift + v (see comments below).