(whoops, i accidentally sent this before finishing. please give me a moment to edit)
Hi Kiyoteru!
Thank you for the very fast reply! I'm currently trying the Homebrew method, and everything went swimmingly until one small hitch. This is going to be a tedious retracing of steps, so please bear with me.
I had successfully installed Wine and was about to open the UTAU installer in Terminal (as the Homebrew tutorial instructed) when I accidentally double-clicked the UTAU installer instead. I'm not sure if that's important or not, but when it began opening in the Wine app instead of via Terminal, I clicked "cancel" to all of the requests for Wine plugins and went ahead with the UTAU install. After it completed, I couldn't find UTAU in the "Program Files" folder, so I tried installing again the intended way, using the command line.
Still, UTAU did not appear in "Program Files" after clicking through the installer. The installer looked different on this attempt and on subsequent tries, too. During the first installation following the accident, the installer window matched the one in your tutorial exactly, with the (E) and (M) options and the directory box. On subsequent tries, the installer window only had (R) and (M) options, and there were also less pages to click through.