This video details a very quick fix to the random issue of "Creating project folder failed" in the Unity Hub when opening a project.
Other notable solutions:
Make sure your Unity Hub, Editor and Project are inside of your C:// drive.
Have another solution? Let us know to help more users.
I first noticed this issue after updating to the 3.4.1 version of the Unity Hub and there seem to be many misunderstandings of how this issue is fixed.
I do believe this issue may have stemmed from changing the name of my Windows 10 account but I have not found an acceptable permanent solution yet. Until then, fully quitting the Unity Hub seems to be the quickest and easiest fix.