I know I know, I have a lot of questions lately. Consider it a healthy dose of curiosity .
I'm running a Mac Mini dedicated with MacStadium.
Specs (not sure if needed)
macOS Sierra 10.12.5
Mac Mini (Late 2014)
2.6 Ghz Intel Core i5
8GB 1600 Mhz DDR3
1TB SATA HDD (not Fusion)
The Machine is running FMS 22.214.171.124 currently.
I was wondering if it's possible to run mac OSX Sever 5.3.1 along side FMS to handle Open Directory.
I thought it would make life easier for me to take care of authentication in Filemaker Pro?
If you don't need OD for other purposes then you don't need it for External Authentication into your FM solution. Just use local accounts and groups in the OS itself (without OSX Server). At least that way you won't have interference of the other OSX Server components (most notably the web server).