The M10 FHD has a 1920 x 1200 resolution on a 10 inch screen. By default, LibreOffice is installed as one of the Xapps, but it is not scaled, so it looks tiny on the high resolution display. I used to scale the documents themselves by using the slider in the lower right corner in LibreOffice Writer, but this was a bit annoying since even if the document was scaled, the user interface was not.
I have found that by simply choosing “Options…” from the “Tools” menu and selecting the “View” tab, it is possible to choose scaling of the whole programme. As with Firefox, I have found that 180% works well. This makes LibreOffice the same size it would be on a 1067 x 667 screen of 10 inches and that works fine. Everything is large enough to be easily viewed, but at the same time there is enough space for content.
I also like to remove the toolbars by deselecting “Formatting” and “Standard” in View > Toolbars and in stead drag the Sidebar out from the right to show more options and be more useful. With the tablet in landscape orientation, this gives me the most space for contents on the page as long as the document is in portrait orientation (which almost all LibreOffice Writer documents are). It gives the least amount of scrolling and the largest possible view of the page. Especially on smaller screens, making the most of the available space is really nice (but I also do this on my 24 inch desktop screen).