There are only a couple obscure routing engines that can route through areas, so you will have to use interconnected linear ways probably.
What square are you mapping exactly?
If the entire square is open to cars, you should do something like the following:
On the square area itself set
place=square
area:highway=yes
Also connect all the other roads entering/exiting the square to each other, so that they are routable; make sure they all have appropriate highway=* tags set, so that routers don't get confused.
Make sure that all pedestrian paths (sidewalks) are also connected together, using highway=crossing when appropriate.
I don't know if it's of any solace, Linux used to be a much more... ahem... "involved" experience a decade or two ago. This was more-or-less the norm:
I can't really say what the newcomer experience is nowadays, but I can say for sure that even in the worst-case (as it was in the times when I started using it), after a couple months of furious issue-fixing and trying new things, you will eventually settle on a setup that works for you. Some people actually get addicted to all the problem-solving and start looking for more issues to fix; some start distrohopping to find a "more perfect setup", getting their fix of issue-fixing in the process. If you're not one of them, congrats, at that point you can (mostly) just continue using it, until you need to update your hardware, then process may or may not be repeated depending on your luck. If you really hate fixing issues twice, you can look in the direction of declarative distros like NixOS or Guix, but I will warn you that the two-three months of furious hacking is still very much a thing here, but after that you're set more or less for life.