There is an old 2017 topic asking this - https://www.geekzone.co.nz/forums.asp?forumid=43&topicid=213917, but I'm guessing the world has moved on with what Spark now describe as a "fibre landline" rather than a landline on ADSL/VDSL that the topic covered. I'm assuming that lodging a porting request for the POTS number to a VOIP provider now has no danger of also terminating the fibre connection with Spark? Anyone able to confirm this?

I couldn't see anything Spark web site addressing this (probably understandably).