With the release of Fantasy Grounds v4.20, I have pushed out a big update to my Syrinscape Sounds extension available at https://forge.fantasygrounds.com/shop/items/117/view
The update primarily benefits Mac and Linux users. FG 4.20 introduced a new API function which allows it to trigger sounds directly using the Syrinscape web API. This means that Mac and Linux users using Syrinscape Online will no longer require any 3rd party URI handlers.
It should all work seamlessly with just Syrinscape Online and Fantasy Grounds installed, nothing else.