To summarise: Create a new Parallels VM by installing a fresh copy of macOS Catalina from Recovery Partition (or use existing VM). DO NOT INSTALL Parallels Tools or uninstall it if it's already installed. Login to iCloud account which have Apple Developer Program membership active (thanks @paulrbarnard). Resize disk drive to be at least 80 GB (see article 112119 in the parallels knowledge base website on how to do that). Download and install your Beta profile (https://developer.apple.com/download/). On a host, supported Mac, run these commands in a terminal (thanks @danfry): sysctl hw.model this will get you mac_hw_model (something similar to MacBookPro14,3). ioreg -l | grep board-id this will get you board_id (something similar to Mac-551B86E5744E2388). 7. In the Parallels VM configuration, under Hardware -> Boot Order -> Advanced Settings -> Boot flags, enter the following (inserting the information noted above where shown): devices.mac_hw_model="mac_hw_model" devices.smbios.board_id="board_id" where mac_hw_model and board_id inside the quotes should be substituted to your values. 7. Proceed with downloading and installation of macOS Big Sur via System Preferences.