I've been dogfooding the iPad layout of Element X under macOS on Apple Silicon since day 1 - it works pretty well. We could also ship it via Catalyst to run as a pure macOS app (albeit with the iPad layout) on both Apple Silicon and Intel, once https://github.com/rust-lang/rust/issues/106021 is fixed.

Unfortunately making it a "real" macOS app is much harder, as the UI is currently uses UIKit in a bunch of places to make up for feature and performance limitations in SwiftUI. These would have to be ported over to AppKit to run on macOS. I had a go at it over the holidays, but it's not trivial - perhaps someone with more AppKit skills than I could make it work (or maintain a fork) though.

To give an idea of the amount of UIKit that would need to be swapped out:

    matthew@shadowfax ElementX % find . -name \*.swift | xargs perl -ne 'while (/[^a-zA-Z](UI[A-Z].*?)[^a-zA-Z]/g) { print "$1\n" }' | grep -v UITest | sort | uniq -c | sort -rn
      52 UIKit
      31 UIImage
      20 UIApplication
      13 UIScrollView
      12 UITextView
      11 UIDevice
      11 UIConstants
      10 UIColor
       5 UIViewController
       5 UIRectCorner
       5 UIKitBackgroundTask
       5 UIKeyCommand
       4 UIView
       4 UIPasteboard
       4 UIBackgroundTaskIdentifier
       3 UIViewControllerRepresentable
       3 UITableView
       3 UIScreen
       3 UINavigationController
       3 UIKitBackgroundTaskService
       3 UIFont
       3 UIActivityViewControllerWrapper
       3 UIActivityViewController
       2 UIViewRepresentableContext
       2 UIViewControllerRepresentableContext
       2 UITextViewWrapper
       2 UITableViewDelegate
       2 UIResponder
       2 UIHostingController
       2 UICollectionView
       1 UIViewType
       1 UIViewRepresentable
       1 UITraitCollection
       1 UITextViewDelegate
       1 UITableViewDiffableDataSource
       1 UITableViewController
       1 UITableViewCell
       1 UIScrollViewDelegate
       1 UIKitAttributes
       1 UIHostingConfiguration
       1 UIContentSizeCategory
       1 UIBezierPath
       1 UIApplicationDelegateAdaptor
       1 UIApplicationDelegate
       1 UIActivity