2.0.4.24 (which had build issues and was replaced) raised the mono requirement to v5 which is avalable as Mono v5.18.0.240-12 from SynoCommunity packages. I’m not positive the hardware model coverage is as good, and if it’s not then there’s an issue. mono 4.6.2 is from Nov 2016 and is inadequate for many reasons. Maybe there are other places where mono for Synology can be obtained. I don’t have one and am no expert.
@drwtsn32 actually has a Synology, but I think recently moved to a Docker with some sort of recent mono. Perhaps we could find out what that one had, and get some better ideas of mono v5 availability for Synology.