Styling scrollbars can often be challenging due to varying levels of support across different browsers and devices. On iOS, including devices like the iPad Mini, customizing scrollbars is quite limited compared to other platforms because Safari, the default browser, does not offer much inherent support for this.

In general, native styling of scrollbars through CSS is primarily supported in WebKit browsers (like Chrome and Safari) using vendor-prefixed pseudo-elements like ::-webkit-scrollbar. However, even with this approach, iOS Safari is known for not fully honoring these styles, limiting your ability to implement custom scrollbar designs directly via CSS. Unfortunately, Bootstrap 5.3.3 does not include built-in utilities or components specifically for styling scrollbars, especially for iOS devices.

For web applications targeting iOS devices, if you wish to achieve custom scrollbar designs, you might need to consider alternative methods:
JavaScript-Based Solutions: Libraries such as OverlayScrollbars or SimpleBar can provide cross-browser custom scrollbar functionalities, including in environments like iOS where native CSS styling isn’t fully supported.
Progressive Enhancement: Design your application to be fully functional without relying on custom scrollbar styles, ensuring usability, and apply custom styles or scripts only in environments that support it.
WebKit CSS (Limited): You could attempt to style scrollbars using ::-webkit-scrollbar and related pseudo-elements, with the understanding that they may not be effective on iOS. For other devices with WebKit support, this method allows some level of customization.

Ultimately, while direct CSS customization of scrollbars on an iPad Mini using Bootstrap isn’t natively supported, employing a JavaScript library is a practical workaround to achieve consistent cross-platform design.