Anything that prevents you from playing the game properly. Do you have issues playing for the game, downloading it or successfully running it on your computer? Let us know here.
This may be a niche thing, but I wanted to run factorio headless on FreeBSD 12.1. Since there is no BSD build of it I tried it with the linux compatibility layer, but linux_base-c7 contains libc 2.17. Factorio needs 2.18+, so it can't be run in the linux compatibility layer it seems.