Also reported here:
It would seem you have installed some custom theme or dashboard (via HACS?) at some point that auto creates an input select helper from your existing dashboards, so presumably you could change dashboard from the frontend. The ‘refresh’ option either updates the helper, or perhaps refreshes the dashboard? This is definitely not a core feature by the way.
I’m absolutely speculating here, but it’s probably choking on the new to 2026.2 default overview dashboard and the legacy one, deriving them both as ‘lovelace’ and trying to add that twice as an item for the auto created input select, which obviously won’t work.