HA tenancy in STBX name - what options?

[Gloriously]

This is a Q for DB.

His STBXW of 12 years remains in the family HA home with their 2 DC. It was her tenancy before they met and married with her previous DC (now adults who have left the home).

DB has left the marriage and understands that his name is not on the HA tenancy.

Is he likely to have any scope with the HA for alternative housing due to living at the property for 14 years but not on the tenancy?

I doubt it
but he should speak to the HA to find out where he stands

Your brother can apply for housing with the HA the same as anyone else can!

He won't get additional ranking because he's lived in a HA tenancy; no.

He can join the list like everyone else, but in most of the UK, the waiting lists are several years at best, and a single adult male would be quite low priority. He may get emergency assistance if he's homeless and has qualifying vulnerabilities, but that might be at a homeless shelter or the like.