I’ve been facing this issue for some time. It made me go crazy, I’ve even been thinking about quitting Zwift because of that. But last weekend I spend an afternoon on debugging this and fortunately I was able to figure things out.
On my laptop I’m using Ubuntu 20.04, however I think this may be more driver related issue and to get rid of this Error popup and make Zwift starting and operating properly all you need to do is to locate “prefs.xml” on your computer (it is a xml file with Zwift settings saved in it) and remove line:
without this line Zwift doesn’t show up any error messages and works ok, unfortunately this must be done before every Zwift ride (but I think it is not a big deal to prepare some automated script to remove that line)