Not sure if this is something you can fix or not, but Blazorise components don't get scope attributes added so CSS Isolation doesn't work.
Test.razor, add a Blazorise component and a plain HTML element.Test.razor.css file, and reference <Root namespace>.styles.css in your index.html as described herebackground-color: red; or something else obvious, add the class to your blazorise component and the html element.I tried it and you're right, it's not working. The reason I suspect is that Blazor does not generate a special attribute with a random ID for custom components.

I will try to investigate more but for now, it's low on a priority list. Maybe for the next mileston.
If you wrap your pages/components in a <div/> and use deep:: in your css/scss, then css isolation mostly works.
If you wrap your pages/components in a
<div/>and use deep:: in your css/scss, then css isolation mostly works.
Here's how you do it.
::deep .myclass {
color: red;
}
The Div is very Important