We need to see the use cases where scrollbars are being used.
- To quickly skim through the content available on the screen
- To continue reading once a person has reached the bottom of the page
- To quickly navigate to the bottom of the page.
With regards to all these actions,the positioning of the scrollbar has an impact and though there has been some debate over the optimal placement of the scrollbar with regards to reading to left to right, it has been established as a defacto standard that the scrollbar is generally on the right due to the conventional standard of reading from left to right and enabling a design element at the end to allow for quick navigation.
I am also going to steal from @Glen Lipka's excellent answer (from the question linked above) about why the scrollbar might be placed on the right.
I think of this more as a mental model issue. Imagine if there was no
mouse, but rather you were doing it with your hand. Most people are
right-handed. My mental model is that I am moving the scrollbar with
my right hand. Therefore, scrollbar on the left would indicate that my
arm is moving across (in front of) the content and blocking my vision
so I can scroll the page.
Of course, the mouse makes this ONLY a mental image and not actually
blocking my face. However, as I imagine the scrollbar on the left, I
keep feeling like I am reaching over the content to scroll, rather
than scrolling from the side.
This paper why scrollbars are on the right and other stories states
The right-hand side looks right because to grab a scrollbar on the
left, or to press a button on the left would mean your hand would have
to move across the screen. Wait - of course your hand doesn't really
have to move across the screen, the mouse does, but it feels as if it
would have to! In fact, for a touch screen, light pen or stylus the
right-hand side is a good idea, but not on-screen
Please read the whole paper for the historical perspective.
However this does raise the question about what would left handers do and I believe the answer to this would ideally be a reversal i.e. place the scrollbar on the left but its a case where economic incentive would trump usability.Taking this quote from a forum about why Microsoft does not support left sided scrollbars
Bill Gates is left-handed so a priority does exist. Microsoft has
actually spent a couple years and a ton of money on development, but
when it came down to it, there were too many third-party programs
where the companies couldn't or wouldn't invest the time and money to
make the change-over available to the users, and Microsoft can't alter
the intellectual properties of another company.
Coming to your question about what to do in case of your IOS app , I would say it would depend on the balance of deciding between whether we should stick to design standards and place the scrollbar on the left for the RTL language and having users face challenges in hands across the screen to scroll down (considering the high demographic of right handed users) or place it on the right to prevent the overlapping of content but face the possible challenge it being against custom and also the user having to travel in the opposite direction to reading to scroll down
However if you are looking for examples of softwares which have done this for arabic or RTL langauges
If you are using an Arabic Operating System and your Windows locale is
also Arabic, the scrollbar will automatically load correctly on the
left of the browser. If, however, you have a European locale and the
language preference within GMS is set to Arabic, Firefox will display
the vertical scrollbar incorrectly on the right.
Here are some additional examples of RTL text and how it influences design
This Smashing Magazine article - Shalom! Showcase Of Web Design In Israel also has some design inspirations for RTL text specific web design