Searching for anything on iOS Safari returns results as expected, however the header outside the results now shows "Searches: Upgrade" and links to the billing page. This started happening today as far as I can tell. I am currently on the "Ultimate" subscription so there is no reason to upgrade, nor any upgrade options. Appears to have started today.
Kagi should not ask users to upgrade unless they are trying to access a feature which requires a different plan or they are about to exceed their current plan limits. This would also mean on the highest plan these messages are never shown since there is nowhere else to upgrade.