I have exactly zero experience in what work a law office does, but I would think it’s mostly paperwork and email? If so you can do that at no startup costs.
Pick a distro (pop, mint, whatever), and install libreoffice or one of its many variants for offfice integration.
A common misconception is that linux involves a lot of coding. Sure, it can if you want to - all the hooks for programatical access are there, for example if you want to build shell scripts for automation. But you don’t need to. It’s just an option many linux users, myself included, like to take advantage of.
When it comes to convincing you, all I can say is this: It costs you nothing to try.