You can directly enable the use of Metal with the drawingGroup() API.

https://www.hackingwithswift.com/books/ios-swiftui/enabling-...

You can also embed a UIViewRepresentable to "manually" embed a metal kit view inside a SwiftUI hierarchy. Basically use SwiftUI to manage most of it, but use metal to handle a bottleneck somewhere. Here is an example:

https://developer.apple.com/forums/thread/119112