The recent upgrade has rendered my Linux VMs totally useless. It already had issues with video acceleration with the white screen which has existed for years. Now it so slow/laggy/broken that it can not even display top running in an xterm. TOTAL CRAP! I can not believe they sell this product as Linux compatible. My Windows VM of course run fine.
I have found that if you DO NOT upgrade Parallels Tools to 4.1.1 in the Linux VM, it will continue work as poorly as it used to, but at least it is usable.
Parallels Tools is up to 16.1.2. 4.1.1 is like 12 years old. Just exactly how old is the version of Parallels you're using, and what kernel of Linux are you expecting to run it on?
Linux is an OS and it cannot be totally unusable, as there are different technologies that require Linux to work.