I have been running Zwift through wine on Ubuntu 20.04 LTS for the past two years with no problems. I ran Zwift this way as recently as Tuesday 1/11. Today I received the 1.21 update and now whenever I launch the game I get an error message stating I running a version of Windows which is not supported. I double checked my wine configuration and it has been configured to provide Windows 10 compatibility.
Please remove this check for wine users or provide a way to disable it.
Look for a couple of commands after that line - those basically install the required dependencies to prevent the app from crashing. You can run those manually with the correct WINEPREFIX env variable set (i.e. pointing to your Zwift installation folder).