"Since September 2019 all spec violations have been addressed by Apple, as recorded in the next section. The section thereafter - "Peculiarities" lists specific implementation choices by Apple that differ from what most implementations provide, but are not spec violations per se."
That list of "peculiarities" is pretty disappointing. The lack of a discovery endpoint is sad; it isn't that difficult to provide and it greatly reduces the obscurity of configuring RPs.
"Since September 2019 all spec violations have been addressed by Apple, as recorded in the next section. The section thereafter - "Peculiarities" lists specific implementation choices by Apple that differ from what most implementations provide, but are not spec violations per se."
[0] - https://bitbucket.org/openid/connect/src/default/How-Sign-in...