If you simply want to become a priest and offer the Latin Mass, there are multiple options. The question is which of these options is (currently) a manner of seeking Holy Orders in communion with the Pope, and the Church.
First however, there is the fact that the seminary is a program of formation of both mind, and soul. It is a place where both you and your lawful superiors test your vocation. We read in the Scriptures “Many are called, few are chosen.”
As for those priests who are in communion with the Holy Father, and can be either incardinated into a Diocese by a bishop, or permitted to function as a priest, the FSSP, (Fraternity of St. Peter) the ICR (Institute of Christ the King) the Canons Regular of the New Jerusalem, and the Canons of St. John Canthius are four such priestly Fraternities or Canons. The Society of St. John is another alternative, although I do not know if they are currently accepting vocations.
The SSPX are not utilized, or permitted to function as priests in any Diocese at this time, hopefully they will one day soon return to full union with the Church, and be utilized. As it stands now that is not the case. There are other groups some who were founded by Non-Roman Catholic individuals that call themselves Traditional Catholic. There are a couple of groups that broke off from the SSPX, and a few that claim to derive their orders from the late Archbishop Thuc (formerly of Viet Nam) None are currently in communion with the Pope, and some do not recognize the Pope of the Church, claiming that they alone are a remenat of the Church.