If a separation agreement doesn't mention estate claims at all, can a former spouse still claim support from the estate?

Possibly, yes. If a separation agreement is silent on estate claims, there's no release standing in the way — the question just becomes whether the former spouse otherwise qualifies as a dependant under Part V of the SLRA. That test asks whether the deceased was providing support, or was under a legal obligation to provide support (for example, under an ongoing support arrangement in the agreement itself), immediately before death — not whether the couple was still married or living together.

So a former spouse who was owed or receiving support under the separation agreement at the time of death may still be able to bring a claim, even though the agreement never mentions the estate. What the agreement does say about support — the amount, whether it was meant to end on remarriage or a fixed date, and whether it was still in force at death — matters a great deal to that analysis. Because silence can cut differently depending on the agreement's other terms, this is worth reviewing with a lawyer rather than assuming either that silence helps or hurts the claim.