Hi Nico
We have a Synology NAS with 15 Macs and 2 PC's connecting with both AFP and SMB
I found on the Mac side Foxtrot is pretty much the only software that will search the Synology - this was after a lot of searching for solutions and trying to get an answer out of Synology why Macs cannot search them (they were less than useless)
When it works it works very well, even giving previews of documents. But I have found some issues along the way with connection to the index, but that could be network issues our end.
Saying that the Foxtrot guys are good and do read these posts and the app is updated regularly
In my opinion Foxtrot should be better advertised to get more revenue in so they can tweak it faster. We can help with that guys!!!