So, here's the problem, people. If you believe the V2 papal claimants are actually popes, there's nothing wrong with trying to find ways to be subject to the Vicar of Christ. In fact, one is absolutely required to make every possible effort.
It's only if you have the intellectual honesty to admit that, yeah, there's definitely some doubt about whether they're popes, that you can justify a refusal of submission.
Pre-V2 Canonists state that one is not schismatic for refusal of submission due to well-founded doubts about a putative Pope's legitimacy ... the logical corollary being that you are if you don't entertain such doubts.
Now, you do realize also that +Lefebvre, +Tissier, and +Williamson have all stated at various times that it's possible these guys aren't popes ... and such a position suffices to absolve from schism. You know this means they are not actually sedeplenists, right? See, most theologians hold that papal legitimacy is dogmatic fact, meaning that it's just as certain as that God is Three Divine Persons. It's as much a heresy to doubt a dogmatic fact as it is to deny it. If you say that it's possible there are 4 Persons in God, even if you don't commit to it but just say it's possible, that means you do not accept the dogma of the Holy Trinity with the certainty of faith ... and you're a heretic. Same with these papal claimants.
Now, you could say that you give them the benefit of the doubt just in case and obey when you can ...but again that's only if you admit some doubt.
There's a theological maxim that a doubtful pope is no pope, for this very reason.
So if you believe, as +Fellay does, that it's absolutely certain with the certainty of faith that they're popes, not only is he doing nothing wrong by trying to re-enter a state of submission to the Vicar of Christ, but he actually needs to try much harder, i.e. actually do it.
Just be honest that you're not as certain that Prevost is pope as that Christ is God, i.e. that there's some reasonable doubt about his legitimacy ... and save your faith from being shipwrecked with heresy. That's all you need to do ... admit some doubt. Or else consider Father Chazal's position ... rather than slouching toward Old Catholicism as many of you have done.