1) In the EU, if you uninstall Apple Maps and set another app as your navigation default, many (most?) addresses won't work anymore. Clicking an address will show you an alert that you haven't installed a navigation app, or sometimes just open the Maps website in Safari.

2) With the new dual-language keyboards, text prediction is doubly messy. My Dutch-French keyboard suggests English words and almost never understands which language I'm actually typing in.

2b) Fine, but then at least my English keyboard will be okay? Nope. The other keyboards still get polluted with suggestions and auto-correct from the other language keyboards you have. For example, it's now impossible to write “as a” without iOS correcting it to “às à”, even though my Portuguese keyboard is separate and I'm clearly typing in English.

3) Search on iOS always searches for files, even if you remove the Files app contents from search results. (‘App’ just got corrected into ’all’.)

4) In iOS, HealthKit occasionally locks down and the apps that need it to function become unresponsive (AutoSleep, WaterNow, Cronometer). This can only be fixed with a restart.

5) In macOS's Mail, if you Command-Z to undo deleting an email, 90% of the time it goes in a Recovered Emails folder instead of where it was. 10% of the time it's not undeleted at all and is instead completely gone (also from the trash).

6) Calendar.app on macOS can become unusable if you have attachments in events. The solution is to open the event on iOS and delete the attachment.

7) Screen Time asks me twice if I want to unlock an app or website. Sometimes the animation plays and nothing happens, so I have to do it thrice.

8) The Game Mode notification can't be disabled, because no one at Apple has ever alt-tabbed away from a game.

9) If you search for a setting in iOS or the redesigned macOS System Preferences, I think 3/4 of the time it will take you to a nearby screen but not the actual setting. This is because Apple designers don't know that they can scroll you or link you to the right place.

I've reported all these bugs to Apple with screenshots or videos. None of them were ever fixed.