Hi again,
I’m testing columns again, and before I publish an article on the subject, I’d like to check with you.

Find attached my testing environment, env_test.tex, and columns.tex, a "product", as well as the result of compiling with —mode=oldcolumns,grid and —mode=grid

The "oldcolumns" example shows the result of \usemodule[old-columns] and looks like it should. The new columns code still has errors:

Previously it wasn’t possible to start (new) columns mid-page, i.e. after an image or chapter/intro like in the example.
This works now (progress!), but the pre-columns stuff is still shifted to the right. (And I don’t know where the yellow box comes from.)

Additionally, footnotes in old-columns use the whole width and don’t interfere with the text columns, while in new columns, footnotes start in their column but use the whole width anyway and thus interfere with the main text.
I tried \setupnotes[footnote][location=columns] (and other options) but saw no change.

Many more options to check…

Best, Hraban