There's no way to know either way. All we can do is have our suspicions.
If a priest is good and teaches the truth and gives me spiritual food I don't really mind if he is validly ordained or not. What difference does it make to me?
If a NO priest is a clownish fool and my children take that to mean that the Catholic Church is stupid, irrelvant and silly, (which is what happened after Vatican II) then what does it matter that he is validly ordained or not?
The gulf between Trad priests and NO priests is so wide in terms of what I can see and hear and judge for myself that it seems petty to worry about stuff I cannot know like whether an ordaination is valid.
If genetic engineers could make healthy, nutritious grapes grow from a cow's ass or a mushroom covered rotting log and they were biochemically indistinguishable from normal grapes then I would buy them and eat them. I wouldn't sit around debating whether they were valid grapes or not.