Subject for the Second film?

[Sauron the White]

from Morthoron

they cannot use part of the LotR appendices either (those parts that deal with events in the 1st and 2nd age, and which are covered in the Silmarillion

That opinion goes against every single thing I have ever heard - including long debates on this site - about what rights Zaentz purchased. My understanding is that he bought cover to cover rights with nothing exempted. That would include the Appendicies as written but no more.

I would point out that the film rights were sold BEFORE the publishing of the SIL.

If you have factual documentation to support this new, far more restrictive viewpoint, I would love to read it.