I still have a couple clients that run FileMaker 11. They're more than willing to jump on the bandwagon and install the latest and greatest version of macOS, but not FileMaker for some reason.
I tried a couple things today after Apple released the installer so I could warn them before they did something stupid.
First - An iMac running macOS Sierra, had FileMaker Pro Advanced 11 on it already. Ran the macOS installer to take it up to macOS High Sierra. I had to re-add the favorites as this was a non-production machine. When I add the address AND a name, instant crash when I exit the dialog. If I add JUST the address, no crash. Adding the name causes a crash. I was able to open files. Exiting out of Manage Database caused a crash.
Second scenario - installed macOS High Sierra on to a fresh VM installation in Parallels 13.0.1. Installed FileMaker Pro Advanced 11. When I try to launch I get an error saying that the application was "installed incorrectly or modified by another program. Please run the installer to get a fresh copy of the application after determining the cause."
Of course, your mileage may vary.
I've since warned clients NOT to upgrade to macOS High Sierra, especially if running older versions of FileMaker.