ods actually already works.. it goes through the same SheetJS path as xlsx and csv. But your question made me check properly and there's a bug... I never registered the OpenDocument mime type so Gander wont show up in the "open with" list when you tap a .ods. Opening it from inside the app works fine.

Fixed in the manifest just now, it'll be in the next build.

odt and odp dont work at all. odt is a fair ask.. its the same shape of problem as docx so it's doable. Less sure about odp though.. the pptx renderer is already the weakest part of this.

And yeah, fewer apps on the phone was pretty much the whole reason I started building this.