Hi again @petrichor and to others who may find this info useful. The suggestions from my adult child (who is f to nb transgender and had top surgery in 2019) are :
Transgender and Gender Diverse Families Australia (includes partner relationships);
Western Sydney trans support group (depending on where you are there are similar groups online for many places);
Online peer groups for whichever state you are in;
PDF resources for partners on Rainbow Families website (you may find a specific one that speaks to your situation).
A family can be partners, doesn't have to have children.
They went on to say : There is space and love for you somewhere, you will find it. You deserve that. And to be known for yourselves ... and articles by trans people who talk about their partners, podcasts too. But also, no one other's story will be the same as your story.
A lot here that can be found googling.
Hope any of this is helpful for someone out there.