https://evisa.gov.vn

From Sydney:

Vietnam Airlines or Vietjet Air: 1 stop in Ho Chi Minh City

From Brisbane:

VietJet Air: 1 stop in Ho Chi Minh City

or Jetstar/Qantas to Ho Chi Minh City, then transfer to:

VietJet Air/ Vietnam Airlines/ Bamboo Airways reaching Phu Quoc Island.

From Darwin:

Fly to Singapore, then take Scoot to Phu Quoc.

From European countries :

Airalo for eSIM

Grab is commonly use for transport or food delivery.

Google Maps and Google Translate