How can I convert SCF trace files to ABI files?
Apparently convert_trace does not do a good parameter checking and silently sets ZTR as default if it does not recognise a valid output format.

I don't know of any freely available command-line converters in that specific direction. Even at the height of Sanger sequencing (late 90s, early 2000s), pipelines usually tried to reduce complexity and footprint by converting AB1 to anything else, often SCF (ZTR came too late and never got enough traction).

That being said, I dug out an SCF I had from 1997, loaded it into Geneious, and re-exported it as .ab1. I was a bit astonished to see that this worked. So Geneious (or similar packages from other companies) may be your best bet for a quick, one-off thing.

Depending on your needs, you might want to think about other ways: either expand BioPython to read SCFs, or maybe to expand the Staden io_lib to be able to write .ab1 (James still maintains that package and is extremely helpful).

Good luck.