The MudBlazor docs instruct users to apply the following to either index.html or _Layout.cshtml/_Host.cshtml.
My Question:
- Can I apply the MudBlazor theme to a subset of pages/components? And keep Bootstrap in place for the other pages/components?
- Razor Sections seems like a solution, but I haven't gotten them to work:

You could try the following, however disclaimer I have not tried this myself. I'm not sure if this result in conflicts between libraries and because you are loading two libraries there is very likely a performance penalty.
It is possible to configure different layouts for you blazor project.
Create a new layout with
MudBlazorLayout.razorAdd
@layout MudBlazorLayouton top of the pages that use mudblazor.You can configure either Bootstrap or MudBlazor as default.
see learn.microsoft for more details.