The issue you describe is most likley caused by a GPU conflict introduced by Big Sur. You have two options:
1. Disable GPU support in Lightroom Classic Perferences (Performance tab)
2. Downgrade to Lightroom Classic 10 using the Creative Cloud App
Unfortunately, disabling the GPU can result in reduced performance when using some tools within the Develop module (e.g. local adjustments, texture, clarity, dehaze and noise). Therefore, if performance is important, then you may wish to revert to LrC 10. The process is quite simple when using the Adobe Creative Cloud App.
Launch the CC App
Choose All Apps
Click on the 3-dots button to right of Lightroom Classic
Choose 'Other Versions (see below screenshot).
Note that you do not need to unintstall 10.1 as this is handled by the version downgrade process.