I have seen this brought up a few times and from the website the crossplatform native claims are impressive, but I can't find any basic guide or documentation for getting started anywhere. Why is Delphi never a part of the conversation when React Native, Flutter, Ionic, Xamarin etc are discussed?
There's some books by Nick Hodges (former delphi product manager)
'Coding in Delphi' and 'More coding in delphi' for more advanced stuff
The negatives with delphi are its been poorly marketed for years, and it costs money to use, though the community edition is available now. Object pascal is a bit dated imho, but what makes Delphi powerful is the components, there's 2 the VCL which is the original in windows only, then fire monkey which is the new cross platform one.
If you want to see components have a look at tmssoftware.com for some drag and drop components, you can even make web applications with Delphi with their web components (they cross compile to javascript)