If you have Plex pass you have access to the preview build although it's not for the feint hearted, you have to run Plex in a docker container (which is actually how Plex themselves recommended you actually run Plex anyway these days).

I just looked at the specs for the DS416play and it says it has iGPU which is what is required, you could tell for sure by ssh-ing into dsm and checking if there is a /dev/rdi/renderD128 device, if there is then you should be good to go.

I ended up having to write a synology application to start the docker container because the synology docker interface removes the required device mapping when it starts a container, so it has to be started from the command line. My app allows it to start up from boot with the device mapping.