Is there an equivalent `\input{file.tex}` command (from LaTeX) in Typst?

[quachpas]

The correct function is include, but you are setting the page element.

This behaviour is not very well documented, but you can read at the page setup guide

If you make changes with this set rule, Typst will ensure that there is a new and conforming empty page afterward, so it may insert a page break.

A crucial difference to remember is that include evaluates the file and returns content, whereas import will return a module (from which you can select functions, etc.). See Scripting – Typst Documentation.