Pacific Airlines are a “low cost carrier” based in Vietnam - I used them recently between Taipei and Saigon. They also served Kaohsiung and Hanoi. Qantus recently bought a stake.
Unfortunately they have just cut their Taiwan routes - all flights cancelled. No news of when they will resume, but from a conversation with their office, it seems it won’t be for a while.
If you have a ticket, you should contact them. They will try and reroute you via EVA.