In Android there's an option to lock orientation.

I believe it is either "force portrait" or "autorotate", there is no "force landscape".

You flip it landscape and turn off autorotation.

When my phone was updated to Android 9, that toggle became force-portrait. If I enable it now, it immediately turns back to portrait and disables rotation.

I'm on AOSP Android 10 and it works as I described. Can't remember the behaviour on 9. Have a good one.

From Android 10 or maybe 9 on the side of the soft keys bar appears a little rotation icon when you flip the device.

Found the explanation: https://9to5google.com/2018/03/07/android-p-rotation-button-...

There's one in iOS as well.

Only for portrait mode. Never made sense to me why they only allow locking in one orientation and not landscape.

It's "lock rotation", not "lock portrait". If you have the device in landscape when you lock it, it will lock in landscape.

I just did it on an iphone 6S Plus and an iPhone XS both with ios13+, and while in landscape, if I press lock rotation, it changes to portrait and then locks it.

I’ve experienced this since iPhone 3G or iPhone 4, so I assume this is how they have designed it.

https://discussions.apple.com/thread/8237975

This website shows a workaround for it:

https://www.igeeksblog.com/how-to-lock-rotation-in-iphone-la...

No, the feature is called "Portrait Orientation Lock" - it will only lock it in portrait mode and not landscape.

https://support.apple.com/en-us/HT204547

Not all video apps respect the lock orientation setting