I've used LibreOffice for a good decade now, but it can be damned annoying sometimes.
For example, you're drawing plans for redoing a room that's 8' long by 5' wide (a tiny bathroom).
Go to Tools → Options → LibreOffice, then, in the Type to search edit field, type "unit." This will get you here:
...and you can select Unit of measurement: Inch plus set the Drawing scale: to 1:12.
Right-click rulers (top and/or side) to choose what scale (Inch or Foot). If you're doing odd, inch-specific lines, then turn off snapping to grid (View → Snap Guides... → Snap to Grid).
This will set it up so that, for a plan that's 8' wide, it really won't fit in portrait mode. Solution is to change the scale to ½ (1:24) or switch the layout to landscape mode. To do the latter, go to Page → Page Properties... → Page → Orientation: Landscape.
To adjust thickness of line drawn, select the line, then right-click on the line (to get context menu) and choose Line... → Line → Thickness: +.