I notice you're asking about a "portable" version of BricsCAD 2021. I should clarify a few important points before providing guidance:
The term "portable" in this context usually refers to third-party, unauthorized versions designed to run from a USB drive without installation. Using such versions is generally discouraged due to security risks and lack of technical support. BricsCAD V21 (2021) Technical Report 1. Software Overview Core Engine : Native .dwg format, highly compatible with AutoCAD files. Platform Support bricscad portable 2021 2021
BricsCAD Portable 2021