I normal case changing from ‘windows’ to ‘legacy’ and ‘legacy’ to ‘windows’ will work through project.json file change on one condition All dependency should be compatible with the target framework.
In the below I changed the project from ‘legacy’ to ‘windows’ (means .Net Framework4.6.1 to 5.0) but UiPath.PDF.Activities are not compatible with it.
As per the your above screenshot ‘System.Private.CoreLib’ in your Main.xaml is not compatible with ‘Legacy’ I guess. can you please confirm?
Yes in order to use all UiPath Packages, I recommended to use ‘Window-Legacy’ since it will be compatible with .Net Framework 4.6.1 onwards.
Hope you got an idea behind this compatibility modes. Thank you.