I've just installed 11.0 Beta (20A4299v) on Parallels 15.1.4 without encountering any of the issues above. It did take me a few goes to get it right. Firstly you need a lot of free disk space. I had 40G free but it complained. I increased the size of the disk to have 60G free and it was then fine. I then encountered the problem of the login failure with black screen and eventual return to the login screen. After a bit of experimentation I discovered that you need to have the AppleID that you use for developerID signed in on the existing OS running in the VM before you do the update. It's possible there is some authentication going on behind the scenes. It's now running quite nicely.

You will need to recover from your back up. Reboot and press CMD R keys as the computer reboots. This will give you the option to recover from your backup.

ARECA thunderbolt RAID devices do not work with Big Sur public Beta. Areca are aware of the issue but do not provide a solution. If you are stuck with not being able to access your data after installing the beta you can do the following Using Areca RAID on Big Sur Beta Copy ArcMSR.kext from /System/Library/Extensions to /Library/Extensions You can now manually launch the RAID support by typing the following command in a terminal window sudo kextload /Library/Extensions/ArcMSR The RAID will show up in finder The support will be lost on each reboot. To automate the process To automate the process on bootup a few things need to be done 1 - Enable sudo support for the required commands without password open a terminal type sudo visudo /etc/sudoers use the arrow keys to scroll down to place the cursor on the line directly below the section User privilege specification root  ALL=(ALL) ALL %admin ALL=(ALL) ALL Type i to enter insert mode Type  ALL username = NOPASSWD: /sbin/kextstat, /sbin/kextload (note usernameshould be your username as shown at the start of the prompt line in the terminal) hit return key Type :wq hit return key The sudoer file is now updated to permit execution of the two needed kext commands without entering a password 2 - write a script to run the required commands launch Script Editor. The easiest way is to use cmd space and start typing Script Editor in Spotligh Search Create a new file and type the following try do shell script "sudo kextstat | grep \"com.Areca.ArcMSR\"" on error do shell script "sudo kextload -v /Library/Extensions/ArcMSR.kext" end try Save the file to a suitable folder. I used my home folder. I called the file areca_kext.scpt You can test the script by running it from within the Script Editor. You can tell if it works as the RAID will become visible on your system. You can also use a terminal and run the command sudo kextstat | grep “com.Areca.ArcMSR” If the script worked the command will show the ArcMSR kext as being loaded. 3 - Create a launch Daemon to automatically run the script Using a text editor create a file ~/Library/LaunchAgents/com.areca.kext.plist (note: This makes support available for the logged in user only. To have support for all users place the plist file in the /Library/LaunchDaemons folder instead. I have not tried this approach) add the following text to the new plist file <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict>     <key>Label</key>     <string>com.areca.kext</string>   <key>ProgramArguments</key>    <array>    <string>/usr/bin/osascript</string>      <string>/Users/username/areca_kext.scpt</string>   </array>    <key>RunAtLoad</key>     <true/> </dict>  </plist>  The Label attribute should be the same as the Deamon file name and the second string in the ProgramArguments array needs to be the script file you created in step 2 Reboot your computer and the RAID should be mounted when you log in. Once support is provided directly by Areca and Apple simply remove the plist file and normal service will be resumed. Hope this helps out some other early adopter who wasn't aware there was an issue...

Happening to me with NSSharingServicePicker