I decided to try Big Sur on this particular computer. I installed BS b5 on it. Although it installed fine the computer is slow from the start of turning it on or restarting it to desktop. I understand there are variables to impact how fast or slow it boots. I discovered Safari would not load pages anymore. Chrome 85 was acting screwy with 6 tabs open at once. After I restarted then Safari started working again. Weird.... I do understand I am running a "beta" version so I expect odd things to work then not work or randomly stop working. Just some observations.

NOBODY...can comment or share their thoughts on the topic?

I guess I am the ONLY person with an iPhone Xr running iOS 14. Ok.....

I have a Synology router running 8081-1 and I have a iPad Pro running 14.0.1. I am frequent Wifi issues on this device. If I look something up on FB or Google something the page doesn't load or news feeds doesn't refresh. I had some random issues but not frequent issues prior to 8081-1. I am not sure if it is an iOS 14 and 8081-1 combo issue. I have restarted the iPad. I have disabled Private Address setting. I have disjoined and rejoined the Wifi. I have quit those Apps.  I am not sure how to resolve this issue and have stability.

I get the same error message on an iMac M1, 2021 desktop. During the install, it get the same message as the OP. What is the fix?