One of my Users created a Kanban List View for Accounts which grouped them by Owner. The original problem was that there were several (deprecated) Record Types that were splitting the records up. I went in and cleaned up the record types so that they were correct. The unintended consequence of this was that the Kanban settings were now grouped by a different Picklist field and I cannot select Owner in the Group by settings.
I originally thought you could only group by a Picklist field so I was surprised she was able to group by Owner, however according to https://help.salesforce.com/articleView?id=kanban_configuration.htm&type=5 it says
To determine how your records are organized into columns, select a picklist such as Stage to group by, or group records by owner.
As I said before, when I get into the Kanban settings, there is no option to group by Owner. I also did not see an option to group by Owner before the Record Type cleanup.
A search for how to group by owner did not return any useful insights and I know of no other way to alter Kanban group settings. Does anyone have any insight?