Welcome to the Code Crew community.
Keeping up with the latest versions of everything is a problem we all face and eventually hardware does limit you.
If you were keen to start becoming acquainted with SwiftUI then you would need to be running at least macOS Catalina and that would allow you to have the latest version of Xcode which is 11.6
That impacts on what hardware options you have. I have a 2015 MacBook Pro at the moment which I think will be able to run macOS Big Sur when it is released (I could load the Beta version but I prefer to wait) which means I can load Xcode 12 and that will allow me to take advantage of the updated version of SwiftUI.
“Keeping up with the Jones” comes at a cost of course so if finances are not permitting then you have to make decisions around that.
The courses that Chris currently has on offer should be able to be followed along using Xcode 10.1 though I can’t verify that. Chris progressively updates the courses using later versions of Xcode so you might find it a little challenging finding the equivalent options in the Xcode 10.1 interface compared to the lessons that have been created using Xcode 11.x
Long term it depends on what your aspirations are in terms of employment and if you are keen to become a developer. If that’s the case then investing in a later version of a MacBook that will run the current version of macOS and Xcode, will certainly stand you in good stead.