It really depends on what you ultimately intend to be proficient in and whether you want to take on any UIKit work that comes your way or focus solely on SwiftUI.
The vast majority of the codebase in the world is still based on UIKit and to a lesser extent Objective C and still needs to be maintained.
The decision is really up to you.
Bear in mind that the SwiftUI framework has only been around for close to 18 months and has a long way to go in development terms to match the capabilities of UIKit. The reality is that UIKit will be around for many years to come though eventually SwiftUI will gradually be the framework of choice.
If you want to focus entirely on SwiftUI applications then take that path. If you want some flexibility to also take on UIKit work then you’ll need a good grounding in that framework as well.