Qt and Lazarus are fairly equivalent to Delphi and can generate binaries for all of the platforms you mentioned.

Qt Creator is not on par with Delphi’s IDE, although I would Qt on new projects.

Xojo is worth a look. It has the RAD visual form designer approach of Delphi, is a Basic-like language (it used to be called REALbasic & pitched itself as cross-platform Visual Basic), and makes Windows, Mac, Linux & Raspberry Pi binaries. It can also build for iOS, some weird Web deployment that I've never tried, and Android is in the works. There's a plugin architecture like Delphi had & ways to drop down to native APIs if something isn't supported.

The IDE is best on Mac though. The Windows IDE works, but it feels like the developers are probably all on Macs & not really dogfooding the Windows version as much.

[1] https://www.xojo.com/

Thanks for the recommendation. Looks like it has a similar pricing model to Delphi, too.

Pricing should be much more sane than Delphi's current model - Xojo is $99 for one desktop platform (without SQL plugins), or $299 for cross-compiling to all desktop platforms.

Ignore the "per year" pricing - you can choose not to auto renew & keep using the version you've purchased. You only need to renew if you want IDE / compiler updates (they typically release 4 updates a year).

Delphi can produce native binaries for the major platforms: Windows, macOS, Linux (Currently Enterprise version only, requires third party library for GUI), Android, iOS. The free Community Edition supports the platforms above, minus Linux.