Just to point out collabora office available on android, through the obtainium app in f-droid. It’s an android fork of libreoffice
It’s not bad. Collabora’s spreadsheet requires a double click to edit a cell. I can’t begin to guess how many times I’ve clicked in a cell, started typing, only to find the cell still empty because I didn’t do the one thing that other spreadsheets don’t require - a flippin double click.
If you want a cloud option, Cryptdrive is pretty good. https://cryptpad.fr/drive/ Web based so should be good on any platform, docs can be downloaded and edited locally if you want.
I use Cryptpad and it’s awesome, but admittedly the mobile UI is atrocious. I use it anyway but arghhh lol. Is it the only open source, cloud based, collaborative editing office suite out there? I think it might be, right? Worth the headache for that.
I’ve been using dDocs which someone recommended here and it works great on my android (not an app, which I like). Just throwing out another idea alongside yours!