To avoid the logo bar in Power BI reports and dashboards, you have to rely on Power BI Embedded or some other custom embedding technique. There is scope in the API JavaScript of Power BI, wherein, while embedding Power BI reports in your application, you can control the visibility of an element like the logo bar through the embedConfiguration object. We need to set navContentPaneEnabled to false so the navigation pane can be hidden and, in specific scenarios, the logo bar.
Suppose the report is being embedded into a webpage or application. In that case, it can be made more precise using CSS as it can be within an iframe, or you can directly apply CSS rules to hide the logo bar when it's, in fact, rendered within your application. Of course, these will be case-specific and usually limited, and then you dive into the DOM structure to play around a bit.
There is no way to switch the logo bar off if you are viewing reports in the Power BI Service, as this option does not exist. Customizations in such a scenario depend purely on the embedded view, where you have much more control over its presentation. Of course, this has to be done within the schema of licensing requirements and should not deviate from what may be construed as adverse to the terms of service of Power BI.