Hi!
Can anyone advise Free office for android? It strongly wanted to be open source and can work without internet.
I had already tried Andoid open office it is not working (no GAPPS on tablet) and I tried Collabora office (it is working, but not creating files (infinite loading)
Try OnlyOffice, that is the only one that works for me on android.
To be honest, I just prefer doing all these tasks on the laptop since on a phone, these Office things are just super inconvenient on a phone.
The optics of your business associate typing away on the phone while people are talking does not make an endearing image.
Your phone is a very personal device and while you are looking at it, it looks like you are attending to your personal affairs rather than the business at hand.
If you have to do it by phone, make sure it looks like the old fxtec phone with integrated keyboard.
OP said this is tablet 
Unfortunately not everyone have a laptop
Office Suite mod. Personally I cut off everything online from it and make free “premium”. I won’t share it here, unfortunately (because of rules)
Another alternative would be to connect to a web version of either OnlyOffice and LibreOffice.
Consider selfhosting either of those. You can also remote to it via a cloudflare tunnel or through ZeroTier/Tailscale
I would not bet on only office:
https://reports.exodus-privacy.eu.org/en/reports/com.onlyoffice.documents/latest/
But it is always a trade off.
Until I find a alternative to komoot for example I have to hold on to it…
Just for reference the link above