What is SSPX?
The Society of Saint Pius X (SSPX; Latin: Fraternitas Sacerdotalis Sancti Pii X, FSSPX)[a] is a canonically irregular traditionalist Catholic priestly fraternity founded in 1970 by Archbishop Marcel Lefebvre.[6] Lefebvre was leading traditionalist at the Second Vatican Council with the Coetus Internationalis Patrum and Superior General of the Holy Ghost Fathers until 1968. The society was initially established as a pious union of the Catholic Church with the permission of François Charrière, the Bishop of Lausanne, Geneva and Fribourg in Switzerland.
The society is named after Pope Pius X, whose anti-Modernist stance it stresses,[7] retaining the Tridentine Mass and pre-Vatican II liturgical books in Latin for the other sacraments. The society's current Superior General is the Reverend Davide Pagliarani, who succeeded Bishop Bernard Fellay in 2018. Several organisations derive from the SSPX such as the mostly American and effectively sedevacantist Society of Saint Pius V (SSPV) and the canonically regular Priestly Fraternity of Saint Peter (FSSP), that Pope John Paul II made into a society of apostolic life in 1988.
Here is the website https://sspx.org/en
I agree with you that it would be good alternative for Catholics.