Can you please run
sudo apt --fix-broken install
Once that is done, run
sudo apt update && sudo apt full-upgrade
Next, try
sudo apt install winbind
If it fails again, this may be due to the Samba Devs having applied a security upgrade patch not long ago that was known at the time to unintentionally carry over a 21.04 dependency into the 20.04 repository.
The workaround was to completely uninstall Samba - reinstall it, then install Winbind.