I have a managed package with permission sets included. I also use
custom setting objects.
userPermissions have to be set to allow CRUD on
Custom Setting but this can not be included in a (managed) package.
So I decided to update the permission sets in a
post install script but we are not allowed to update Permission Set from a managed packaged (https://developer.salesforce.com/docs/atlas.en-us.packagingGuide.meta/packagingGuide/packaging_perm_sets_profile_setttings.htm)
First error: Update failed. First exception on row 0 with id 0PS0Y000001Ozy8WAC; first error: CANNOT_MODIFY_MANAGED_OBJECT, Cannot modify managed object: entity=CustomPermissionSet, component=0PS0Y000001Ozy8, state=MANAGED_INSTALLED: 
Do you have any idea/workaround for this ? It is not possible for us to migrate every
custom setting as