No, OA, it is not a question of the FORM for the new rite of ordination of priests FOR THE SSPX OF OLD OR THE RESISTANCE. This is everything to do with Sedevacantism!

No it doesn't. A positive doubt of the new-church's sacraments does not (directly) lead to sedevacantism. Mutually exclusive.
Archbishop Lefebvre and the SSPX do not, and have never, held the officially promulgated new rite form of priestly ordination to be invalid.
That's mainly because of the issue of time. +ABL could not write-off all new-ordinations as invalid because some of them were done by valid novus ordo bishops.
In the same way, that's why +ABL never said all novus ordo masses are invalid...because AT THE TIME (70s, 80s, 90s), you still had valid novus ordo priests/bishops, who, if they used the TRADITIONAL CANON, even in the new mass, it could be valid.
Ultimately, the problem with the new-sspx is that it did not update its philosophy on new-rome once all the old, valid, novus ordo priests died. Now that new-rome is 99% filled with new-rite bishops/priests, the "positive doubt" about such is VERY GREAT. I don't see how anyone could argue otherwise.
PlenusV, you're making an argument based on decades-old data. This is why it's faulty.