Android 11 is not available for Genymotion Desktop yet, but it will be available in the future. We don't have any ETA, but check our blog for the latest news.
If you do not want to wait, we have released an x86_64 Android 11 image for Genymotion Device image (PaaS).
For more details, please refer to Genymotion Device image (PaaS) user guide.