Delphi's FireMonkey framework offers cross platform on Android, iOS, Windows, macOS, and Linux with a single codebase and single UI. It works similar to how Flutter works in that it uses DirectX, OpenGL, OpenGL ES, and Metal API to draw the native like controls. Plus offers access to some native controls (mixed together) On Linux it uses GTK+.

There are thousands of hours of video tutorials on how to build cross platform apps with FireMonkey on YouTube. But really it is just all built into the IDE. Select the platform. Compile. A Linux machine and a macOS machine are required to compile for those platforms. Because it is an integrated IDE everyone is together so there is less tooling to fight to compile for all platforms.

Plus Delphi has staying power and plenty of history (25 years) behind it just like Python and PHP (verses newer languages and frameworks which may not be around later).

There are other libraries available for Delphi that let you build apps like Electron (webview based apps) or entirely using native controls on iOS using Storyboards if you prefer that way.

If I can self promote for a second here are 100 cross platform sample apps built in Delphi: https://github.com/FMXExpress/Cross-Platform-Samples