Side panel after software update

Mine defaults to being off. I have to turn on the today/daily view (I tap the third button from the left, the ‘list’ icon, to bring up a side panel. Normally mine is full screen calendar

i looked in the settings for the calendar and don’t see anything obvious to toggle off

The Calendar sidebar cannot be permanently disabled via iPad settings.

If an unwanted sidebar is visible when you open the Calendar App, ensure that the sidebar view is switched-off. Tap/deselect the associated view at the top of the sidebar; when active, the selected view will be highlighted (as shown here):