A: Very minimal. It may leave some temporary cache files in the Windows Temp folder, but it does not install permanent registry keys or Program Files.
While you cannot run Power BI Desktop from a USB stick on any computer, you can achieve a pseudo-portable setup with strategic compromises. Power Bi Portable Version
Power BI Desktop is built on the , depends on Visual C++ Redistributables , and hooks deeply into Windows authentication (Active Directory, Azure AD). Portable apps typically avoid these dependencies; Power BI embraces them. A: Very minimal