I have found three profiles that appear to relate to the same person:
The first of these profiles has a single 'l' at the end of the surname, cited to a Cornish baptism record transcription online (I haven't found an image of the original handwriting). FreeReg also uses one 'l':
Cornwall : St Agnes : St Agnes the Virgin : Register of unspecified type : "Parish Register" database, FreeREG (https://www.freereg.org.uk/search_records/5817d442e93790ec8b3852be : viewed 24 Nov 2022) baptism Joseph Chivel 08 Aug 1823
The transcription of the passenger list for his migration to South Australia and all the South Australian records appear to use Chivell with two 'l's for him and his father.
The merge page flags to make sure the last name at birth is correct. How should I determine or decide which spelling was correct?
Thank you,
Scott
Hi Scott. The parents Joseph and Elizabeth appear to have had an earlier child James, baptised on 22 April 1821 with surname spelt as Chivell. Based on that it would be reasonable to take Chivel as an error and use Chivell for the last name at birth of Joseph (junior).
See this link at Cornwall Online Parish Clerks.