Thanks. I did get it by adding this to my global header:
<link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono&display=swap" rel="stylesheet">
And this to global CSS:
:root {
--d-font-family--monospace: "JetBrains Mono", Consolas, Monaco, monospace;
}
code,
pre,
.hljs,
.cooked code,
.d-editor-input,
.d-editor-preview code,
.d-editor-preview pre,
.markdown code,
blockquote code,
pre code {
font-family: "JetBrains Mono", Consolas, Monaco, monospace !important;
}