Help with CreateSpace package

I want to try using Tectonic with the CreateSpace package (used to format manuscripts for Kindle Direct Publishing, see GitHub - aginiewicz/createspace: LaTeX package for typesetting books ready for I copied createspace.sty into my project directory, and tectonic blows up with this error: no PDF supported engine detected. The error seems to result from createspace.sty checking for specific implementations. Hacking around this is somewhat above my TeX macrology skillset.

Is there a way to have Tectonic masquerade as pdflatex?

No, that doesn’t make much sense to me. If the package author requires you to use pdflatex, you have to use pdflatex, and you cannot use tectonic.

It’s pretty unusual that pdflatex is really required, so maybe the package can be changed to work with other compilers as well, but maybe not. See Make compatible with xelatex · Issue #6 · aginiewicz/createspace · GitHub

This is not a Tectonic specific problem. The CreateSpace package use some low level instructions that are specific to pdftex and can’t be used with xetex (and so with tectonic). You can check this SE question and the comment from @egreg.