This is just a short post brining attention of an excellent and complete refutation of any form of sedevacantism. One way to evade acceptance of Vatican II is too claim that the see of Peter is vacant. This position is not sustainable.
An excellent treatment of the topic can be found here http://www.trueorfalsepope.com/p/peaceful-and-universal-acceptance-of.html#:~:text=The%20peaceful%20and%20universal%20acceptance%20of%20a%20Pope,the%20form%20to%20the%20matter%20following%20the%20election.
Or just type in Peaceful and Universal Acceptance of a Pope. Then click on trueorflasepopr.com
I have to personally thank these authors for their work. They helped my soul out when I was journeying through these issues.