Adamo on Catalunya post-event conference:

Q:
Can you tell us your driver line-up for Australia?
AA:
We had Thierry and Nicolas and Dani and Carlos and we have Andreas and Ole down to do the rally. I firmly believe that we should support the team that has supported us all season. The goal is the Manufacturers’ Championship.

Adamo says he makes decisions "immediately". So I don't think he would change his mind about starting positions after 4 days. Something has quite likely changed

Imo two options:

a) Mikkelsen signed for another team and they either don't want him to start (Toyota) or Adamo got pissed about him signing elsewhere and changed to Breen as he is likely to run some events for them next season

b) Mikkelsen said he is not interested in doing 3-4 rallies with Hyundai next season, without actually being signed by someone yet, Adamo got pissed and changed to Breen for same reason as above