Uno here. We have the same goals: Single Codebase Cross-Platform, targeting Web, Mobile and Desktop (including Linux). Uno runs everywhere .NET runs.
The approach is different where instead of creating an entirely new API, we aligned with WinUI's api (and UWP previously), making it source-code compatible with WinUI so you can leverage the WinUI's ecosytem (CommunityToolkit, 3rd party controls, ...).
By aligning with WinUI, you also get access to all the trained LLMs that already know about UWP/WinUI and therefore also work on Uno.
The approach is different where instead of creating an entirely new API, we aligned with WinUI's api (and UWP previously), making it source-code compatible with WinUI so you can leverage the WinUI's ecosytem (CommunityToolkit, 3rd party controls, ...).
By aligning with WinUI, you also get access to all the trained LLMs that already know about UWP/WinUI and therefore also work on Uno.