I own a Samsung tablet with DeX mode. In that mode, it behaves mostly as a computer, mostly with a keyboard and mouse. Other tablets I had in the post also worked fine with a mouse.

When using Collabora Office, it should become natural to use the mouse as I'm used to in the computer, but it behaves very differently:

1. Click and drag moves the document, instead of selecting text.
2. Right-click does nothing special. In normal touch mode, it's just like "go back" button, and in DeX mode it does nothing.
3. Mouse wheel does nothing.
4. Ctrl+wheel doesn't zoom.

I only used Writer so far. I think this would be a good differentiation, as it seems that only Microsoft Office has some decent mouse support on Android.