Same problem. 2018 15" MacBook Pro i9 running the latest Catalina beta. There is a lot of stuff on my MacBook including HomeBrew, Adobe CC, Pulse VPN. Before trying to upgrade I created a new Volume and installed Catalina beta on it and installed Pulse VPN because that is the only thing I really need to work. Then I upgraded to Big Sur. No problem, VPN worked so it isn't Pulse. I thought that would be the only thing to cause problems. Oh well, time to wait for beta 2.

After removing a bunch of apps and their extensions I was able to do the install. Sorry, I didn't keep a full list of the stuff I removed. I haven't done a clean install in 5+ years so there was a lot of cruft. I removed WebEx, Zoom and Citrix among others. I suspect something I removed from /Library/LaunchDaemons or /Library/LaunchAgents did the trick.

Thank you @luke240 and @dustinrouillard, I used the control-option-shift, wait 7 seconds and hit the power button trick and that worked. I'll update my feedback. It isn't just the System Prefs that get messed up by this either. There are some other cases where MacOS was asking for my password and that was failing.

I had it but it wasn't working (nothing started when I touched the complication) so I deleted the app. Now I can't find it in the app store :(

I performed a factory reset and that fixed it but some number of hours later it was broken again. i just realized that I then re-added the beta profile so need to try this again without adding the profile back