QUAERITUR: Can I attend SSPX Triduum?

From a reader:

I attend the Extraordinary Form of Mass celebrated each Sunday by a priest of my diocese. This is great and I’m very grateful to be able to receive my liturgical heritage as a Catholic each Sunday. However, there will be no EF services for the Triduum; as far as I know, the bishop has never allowed for such provision for our EF community. My question is, given this situation, could I legitimately attend the SSPX chapel for Holy Thursday, Good Friday and the Easter Vigil?
Obviously I do not intend to rupture communion with my ordinary or with the Holy Father in so doing.

Since the SSPX is not in union with the Successor of Peter, I cannot say that people should attend chapels of the SSPX unless they would otherwise be denied, for one grave reason or another, the opportunity to participate at Holy Mass for a significant period of time.