One of the pain points for programming forms for ODK data entry is to open up a matrix-like table structure and span it across so many cascading individual questions in ODK. So a 5x5 matrix results in occupying a lot of screens via broken, one-by-one questions. I am sure it must be on your radar for development. Any ETL for this feature?
Exactly yes. I have added a thumbs-up there, if that's what is needed to show interest. I agree to a lot of opinions already out there, that simple text and numeric will solve most of the requirements.
to achieve something similar I would just use 6 groups with field-list appearances (to display questions on the same screen). Then in each group I would add those four questions. It wont look like a table but it will allow you to collect data.