Getting back to the original post, and subject of the thread, it was about advice for someone who might get questioned by a “SSPX apologist”. My reply was yes, seek out some documentation for specific questions from Catholic sources that are reliable. I also said that the “apologist” likely will anticipate those.
So I suggested add a second plan, ask the apologist some questions about what authority HE or they stand on, when they disagree with the Church. If I talk with Protestants they tend to be far better prepared to question the authority of the Catholic Church, than they are to defend, say, the authority of Methodism, or specifically their particular branch of Methodism, which differs from other branches of Methodism.
I think most people would say SSPX people are more ready to question certain aspects of RCC authority than they are to defend basis of SSPX authority, or rather, to defend Fr. Davide administiration as opposed to other leaders who claim true SSPX,. outside that structure.
So, rather than posters responding to defend or attack SSPX, lets see posts giving practical advice for the OP to respond to that apologist.