Unfortunately my drawing options are somewhat limited in Linux.

Uh, how's that? There is lots of drawing software available on Linux, from simple to professional. It depends on what you want to do, drawing, painting, photo editing, etc. Simply search for "linux drawing software" and you will find plenty of options. For simple lines and circles you might even look into LibreOffice Draw.

You probably already searched for "linux site plan drawing". The first (14 year old) result is from AskUbuntu and the first recommendation is Sweet Home 3D [:)] Most of the rest of the search results are for CAD software. Plenty of those for Linux too. In most cases Sweet Home 3D is much easier to learn and you can use it to create impressions of different possible endresults.