When upgrading to macOS Big Sur from macOS Catalina or an earlier version, one thing that will come in handy for you is the macOS Big Sur Migration Assistant as it can save time Installing programs, their settings plus have your cookies from third-party browsers readily available.
Unfortunately, some users report that macOS Big Sur keeps doing Migration Assistant and after investigating, I see that it is caused by Apple (in their attempt to make things easy for upgrading users) and the user by not paying attention when installing as shown below.
With the. macOS Big Sur Migration Assistant, users can save time Installing programs, their settings plus have your cookies from third-party browsers readily available. I can install macOS Big Sur on an external drive to make sure you do not have any downtime due to hardware or software losing support. In my case, Wi-FI was no longer supported so I was stuck at the desk using an Ethernet connection until my USB Wi-Fi stick arrived.