When you search for "Portable AutoCAD 2020" on YouTube, Reddit, or torrent sites, you will find thousands of links. These files are almost always one of three things:
Some providers repackage the AutoCAD 2020 Network Installer into a self-extracting archive. They call it "portable" because it extracts to a folder. However, when you run it, it still attempts to install system drivers, write to ProgramData, and modify the registry. This is not portable; it is a messy installation that will leave your host computer cluttered.
AutoCAD 2020 had multiple service packs and security patches. A portable crack cannot be updated. You will be stuck with all the original bugs, crashes, and security flaws.
Autodesk itself offers AutoCAD Web App (formerly AutoCAD 360).