Problem with site to site connections using Synology NAS

Hi all,
I am having trouble configuring the TailScale client for subnet routing on Synology NAS devices in two sites. Use case is to allow thin clients in Site 1 to connect to remote desktop servers in Site 2.

Site 1:
Client started with “sudo tailscale up --advertise-routes= --snat-subnet-routes=false”

Site 2:
Client started with “sudo tailscale up --advertise-routes= --snat-subnet-routes=false”

Gateway devices are Draytek routers. Static routes are configured for 192.168.xx and via NAS devices.

From a test machine with TailScale client installed, I can connect to remote desktop serves in the remote site as expected. I cannot however, connect from the thin clients for which there is no tailscale client.

DSM version is 7.1-42661 Update 2 on both NAS devices.

I have checked that the TUN device exists (Access Synology NAS from anywhere · Tailscale)

From the NAS devices I cannot ping local or remote tailscale IP addresses.

Any and all assistance much appreciated.

Not sure if it is related, or what Synology DSM version you are on, but multiple folks (including myself) are having issues with outbound connections with the new Synology DSM update (Version: 7.1-42661 Update 2). Outbound Synology Not Working - #6 by H123