Use OneDrive’s "Files On-Demand" feature. Even if you don't have Power BI installed, you can preview .pbix files in the OneDrive web viewer. More importantly, the Power BI Report Server (on-premises) allows you to upload files via a browser.
However, by reframing your requirement—from "portable app" to "portable environment"—you have several viable paths. A bootable USB drive with Windows To Go gives you native performance. A cloud-hosted Virtual Desktop gives you flexibility. And the Power BI Service gives you universal access for viewing and sharing. Power Bi Portable Version
For the modern data analyst, the goal isn't to carry a .exe on a keychain; it's to carry your capabilities across any environment. Focus on keeping your .pbix files in a portable source control system (like Git) and your credentials in a portable password manager. The tool itself can stay installed on the machine you trust. For everything else, the cloud has your back. Use OneDrive’s "Files On-Demand" feature
You author or upload your .pbix file to a Power BI Workspace (Premium or Pro license required). You can then edit reports using the Power BI Report Builder (for paginated) or the online edit mode (limited compared to Desktop). And the Power BI Service gives you universal
Use your primary machine to install the tool properly.