Legacy frameworks via concurrency

I set "Switf concurrency checking" to "Complete" (curiosity) and tried to address all warnings. Most of "instances" used in frameworks are non sendable classes (UINotification, etc.). Moreover some SwiftUI instances like plain ScenePhawe enumeration (no associated types!) are not Sendable (which made my enum, using ScenePhase as associated type, not sendable - had to use "@unchecked Sendable extension"). This seems to make concurrent programming (callbacks from actors to MainActor classes, etc.) not trivial.

Does such problem really exist (or is it only my lack of concurrency programming skills)? Is Apple going to address it in some way (like making potentially sendable classes sendable, or implementing struct alternatives)?