What is your favourite mobile phone OS?

[TSNH]

What is your favorite mobile phone OS? You can specify the version in comments.

My vote goes for Symbian Belle

[Jody Thornton]

iOS 12

[Dušan Vićić]

In my childhood, the real deal was the Nokia Symbian OS and Series 60 feature phones.

Nowdays, my favorite smartphone OS are Android 4xx series and IOS 9. Visually perfect in comparason of today's minimalistic OS-es.