Thanks for the post a the details including the screenshots showing exactly what you are seeing. Yes, there are many changes after Liquid Glass.
Your understanding is 100% correct. Rebuilding a UITabBar entirely from scratch is a massive undertaking for a complex app. Because of this maintenance burden and the risk of breaking standard navigation paradigms, replacing the standard UITabBar with a custom view is generally not the recommended path forward.
When the Liquid Glass appearance is enabled, the selected capsule is the system-standard visual indicator for the active tab. The framework enforces this specific visual treatment to maintain a consistent design language and accessibility standard across all the different systems.
Because Liquid Glass relies on a specific compositing and rendering pipeline to achieve that look, standard legacy overrides are often ignored or overridden by the system to ensure the capsule remains visible.
Since you mentioned that disabling Liquid Glass gives you the exact result you want, the recommended approach is to opt out of the Liquid Glass appearance for this specific UITabBar rather than trying to fight the framework or build a custom tab bar from scratch. Please remember that eventually that override will stop working.
If you want keep Liquid Glass enabled, and my personal opinion you should, for the rest of the app but want to alter the tab bar, you can try strictly enforcing a standard UITabBarAppearance to see if it overrides the Liquid Glass compositing for the tab bar specifically:
// sudo code, do not copy and paste
let appearance = UITabBarAppearance()
appearance.configureWithOpaqueBackground()
appearance.selectionIndicatorTintColor = .clear
appearance.selectionIndicatorImage = UIImage()
tabBar.standardAppearance = appearance
I know you do not like the appearance and behavior of Liquid Glass on UITabBar. I would recommend you to try to embrace it or customize it to something you can be happy with.
I understand that this may not be the response you were seeking.
Albert
Worldwide Developer Relations.