The (org-assert-version) seems new, with this check

  `(unless (or org--inhibit-version-check (equal (org-release) ,(org-release)))
     ...

could evaluating (org-release) during macro-expansion cause this
recursive load issue?

>> Could you create a minimal working example to reproduce this issue, by
>> removing as much as possible from the repository while retaining the
>> issue, and then send us a tarball with the remaining files?
>
> Sorry, but the issue is triggered by interaction between built-in and
> non-built-in Org. I have no idea if it is possible at all to create more
> minimal reproducer.

> To be clear, I have no clue at all what is going on. I made some
> relatively innocent changes in Org that added a couple of provide
> statements. I could see things breaking completely, but not __only__
> when built-in Org is loaded. So, any attempt to reduce the reproducer
> steps will be me trying random things - not very productive unless you
> absolutely cannot use the reproducer I provided.

No, sorry I couldn't reproduce it on my system :/

M-x emacs-version
GNU Emacs 30.0.50 (build 5, x86_64-pc-linux-gnu, GTK+ Version 3.24.37, cairo version 1.16.0) of 2023-08-14