Hi, I'm involved in some cross-platform porting efforts to get amazing indie games like TowerFall or Celeste to work on *BSD platforms with great success (Love TowerFall by the way!). This works in most cases where the ports use FNA, but FMOD is a hard stop because source is not available (only precompiled libraries for Linux).
I admit I don't know how much work it is to move to a different sound engine, but just wanted to let you know that wider cross-platform use is a possiblity with open-source alternatives to FMOD. In most cases that I've seen, openal or SDL_mixer are used.