HELP!! So I am trying to figure this one out. In regards to TASKS in #Lightning  what is up with the standard Subject field.

It's a ComboBox in Classic however that is not translating in #LightningExperience - we have a validation rule tied to asking the user to select from the "Picklist" - however there not a list to choose from. What is the workaround here? 

I found this HELP post via a Google search, https://help.salesforce.com/articleView?id=task_fields_lex.htm&language=en_US&type=0 - In the search results there is line that states this: This field is available only when a user relates the task to a contact,not to a lead. 

Thanks in advance!