This is another interesting article, which confirms only sweet lupins are grown as stockfeed.
It says they can also be used in layer diets, at up to 20%.
https://www.riverina.com.au/fileadmin/riverina/documents/Products/grain/LUPINS_fact_sheet.pdf
edit, miss read one bit, both sweet and white...
Interestingly, this is not quite matching up with what I am finding.
For example, in this article https://poultry.extension.org/articles/feeds-and-feeding-of-poultry/feed-ingredients-for-poultry/legumes-in-poultry-feed/lupins-in-poultry-diets/
it states that sweet lupins can be fed so as to make...
I have been feeding some Lupins for a couple of months now, and haven't seen any adverse side effects yet.
They are cracked, which means all the shell falls off, and doesn't get eaten so maybe that helps? I can let you know if I do see any problems, if you like?