@ChrisF
I was able to Compile/Install the "subdirectory" version of Indy 10.6.2 under OSX. If I drop a component(TIdFTP for example) to Form1, indylaz is added to Required Packages, the project is building/running fine. However in my projects I use TIdSync a lot for updating visual components from inside threads. TIdSync is located in /Core subdirectory. If I add IdSync to the uses clauses, the project fails to build(see attachment). Actually this can be reproduced under windows and linux too. The same behaviour it's not present when the "all in one directory" version is used. That's why I prefer latter one. The necessary files can be copied in less then a minute to a single directory.
PS: If it helps, my OSX is NOT case sensitive.
Thanks for the test.
So apparently, it's "generally" working but there are still a few issues concerning the "subdirectories method".
Concerning the TIdSync unit, after verifying it's not surprising: the TIdSync.ppu file is absent (though TIdSync.dcu is present for the Delphi version, indeed). As indicated by JD, we could modify the lazarus package file to add a dependency (i.e. forcing the compilation of this unit during the installation process).
I've just made a quick check between the Free Pascal and Delphi binaries, for comparison purposes. There are a few other missing files, but TIdSync seems to be the more important -missing- one (and I'm not sure all the other ones are really necessary for Free Pascal).
As for JD, I'm a bit puzzled concerning the IdTask unit. This one is compiled and present in the binary directory. There is probably "something else" concerning this problem, and it could be interesting to know which one.
A final word: you can of course use whatever method prefer to install Indy (my goal was not to force anybody to use any particular method) , but I think it would be easier for other people to just use the standard package released by default for Indy: so, fixing it ( especially the Lazarus package file) might help them (if we can identify all the issues).
@Cyrax:
Looking briefly at your package file, the main difference I can see is the "IncludeFiles" section. For what purposes ? Are there any other important changes ?