A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
That sounds incredibly aggravating, and that spacebar glitch jumping straight to cell A1 is a known keyboard focus bug in the iPadOS Excel app when an external keyboard is connected. Since you never want the suggestions anyway, the cleanest fix is to just turn the feature off entirely.
You can fix this inside Excel on your iPad by following these steps:
Tap the File menu (or the gear/profile icon depending on your layout) to open Settings.
Go to Preferences.
Turn off Enable AutoComplete for cell values.
Disabling this should completely stop the popups from stealing your keyboard focus, allowing you to type and use your spacebar normally again.