The following is a verbatim excerpt from an Archbishop Lefebvre English-language confirmation sermon (Date/venue unknown; possibly IHM in St. Paul, Mn).
In this sermon he plainly rejects sedevacantism as schismatic.
Since it is easily anticipated that I will be be accused of quoting out of context, etc., I invite those from IHM chapel in St. Paul to listen to the sermon with me tomorrow after High Mass.
Then there will be no possibility of calling into question context, transcription, etc:
"You know that some people, and, uh, I must say that some priests were with us, and they tried to lead us into schism.
"And they say there is no pope, no pope now, no cardinals, no bishops, no Catholic Church.
"We are the Catholic Church.
"I don't say that.
"I don't accept that.
"That is schism.
"If we abandon Rome; if we abandon the pope, the successor of St. Peter, where are we going?
"Where is the authority of the Church?
"Where is our leader in the Church?
"We can't know where we are going.
"If the pope is weak; if he don't do his duty; it's not good.
"We must pray for this pope.
"But don't say that he is not the pope."
There follows a lengthy dissertation on the case of Paul resisting St. Peter, as well as the condemnation of Pope Honorious, whom the Archbishop also noted never lost the papacy.