Also in regard to "obligation" there is a general rule among traditional clergy that one is "obliged" to attend Sunday Mass if you are within one hours distance from the Church and that you "should" attend at least once a month if you are within two hours.
Now IMO the whole "hidden jurisdiction, the traditional clergy are vagrants and not formally the Church" issue, if true, would have the "obligation" cease since they are acting in the "state of emergency".
Yes, for close to 60 year the only valid Massed, Sacraments, Seminaries, Schools, Bishops and Priests have been brought to us by clergy who are not the hierarchy according to those who hold this opinion.
Of course SVs are not obligated to attend an una cuм heretic Mass any more than an R & R is obliged in their conscience to attend an SV Mass, even if that is the only one available.