Lightroom 10.3 is natively compatible on Apple Silicon devices.
No. Unsupported versions of Lightroom Classic were not designed or tested to work on macOS Big Sur (version 11).
Older versions use 32-bit licensing components and installers and will not be able to be installed, uninstalled, or activated after upgrading to macOS Big Sur.
If you have already upgraded to macOS Big Sur, use the Creative Cloud Cleaner Tool to uninstall older versions.