For the platform-independence, I think it would depend on the tool used.

PageFind precompiler release, on their Github, is available for x86_64
GNU/Linux, Apple Darwin and Windows and aarch64 GNU/Linux and Apple
Darwin.

But if we use a search indexer written in interpreted language, as long
as the interpreter is available, we can run it.

Ihor Radchenko <yantar92@posteo.net> writes:

> Sébastien Gendre <seb@k-7.ch> writes:
>
>> If we use PageFind, isn't possible to not include it with org-mode but
>> have an Elisp function that download it ? Like what Elpy do with its Python
>> dependencies ?
>
> It may be possible - Emacs already downloads tree-sitter grammars, for
> example. But can you do it platform-independently, so that things keep
> working on Windows, Linux, Guix, DOS (yes, Emacs still supports DOS),
> what not?