Hello,
Joseph Steffann was my great-grandfather and I can respond to some of your queries. I'm not sure if you have received any other responses.
The evidence and family accounts (his two daughters were able to give my father many first hand accounts as they remained in good mental health well into their ninties). The informatin we have is that he changed his name on the trip to Australia to fit in better with the German population in Queensland. I'm not sure of the port or ship he arrived on, but he settled in what is now Hatton Vale, Queensland and the first Hatton Vale school was formally established at his house. There was a large German contingent there.
Steffann became Steffan with the birth of every child after the commencement of World War I to appear less German. My grandfather's birth certificate has his father with the double 'n' and his as a single 'n'. Certainly, by the time my father was born all the family were using the single 'n'.
Joseph arrived in Queensland about 20 years before he moved to Western Australia but he lied about it on public records when he applied for citizenship (we have some theories about this). He was previously married to Christina Menger in 1874 in Cologne prior to moving to Australia and had children together, some moved with him to Western Australia. What happened to Christina and some of the children/grandchildren is unclear.
Happy to share information.
Kind regards,