I have a hard time believing the Sub deal will ever comes through TBH, the Aussie goverment have never showned any kind of willingness of confront PRC in the recent years, they were even abit reluctent to join the US-Japan lead security talks. Anyway, Aussie economic growth more or less rely on China nowdays. The europeans wouldnt sell any subs, that is shown by EU's recent warning to Taiwan saying the new referendum might distable the region, ofc after some PRC pressure I would believe.
Japan is still bound by law, so they can't sell, and even if they are not bound, they wouldnt, since that could seriously damage the relationship further, which is already pretty cold atm.
If US are gonna make their own desiel sub, that would be a great disaster for the USNAVY, who have been actively opposing any desiel sub to be built in US, and if newly designed and built in US, I will recon the sub will cost enormusly for the ROC to buy, which in turn will be stopped by the ROC legislature for that very reason.