Backticks are a standard markdown syntax - they’re not Discourse specific. (read more in the commonmark spec).
But, if you want to avoid the backtick character you can indent the code by four spaces, or use the [code] bbcode wrapper:
Source:
This is
some code
Result:
This is
some code
Source:
[code]
This is some code
[/code]
Result:
This is some code