Tailscale unable to connect over UDP


I have set up tailscale on my two nodes; one is Linux runnning inside a virtual machine on my proxmox server another is Windows 10.
The Linux node acts as server and Windows acts as client.
The firewall is disabled on the Linux node and the tailscale ACLs are set with this original rule:

	"acls": [
		// Allow all connections.
		// Comment this section out if you want to define specific restrictions.
		{"action": "accept", "src": ["*"], "dst": ["*:*"]},

This is the output of netcheck:

x@tailscale:~$ tailscale netcheck

        * UDP: true
        * IPv4: yes,<ip address redacted>:44443
        * IPv6: no, but OS has support
        * MappingVariesByDestIP: false
        * HairPinning: false
        * PortMapping:
        * Nearest DERP: Frankfurt
        * DERP latency:
                - fra: 28.3ms  (Frankfurt)
                - par: 28.8ms  (Paris)
                - ams: 32.3ms  (Amsterdam)
                - lhr: 35.2ms  (London)
                - mad: 35.3ms  (Madrid)
                - waw: 41.1ms  (Warsaw)
                - dbi: 128.6ms (Dubai)
                - tor: 128.7ms (Toronto)
                - nyc: 128.8ms (New York City)
                - ord: 129ms   (Chicago)
                - mia: 129.8ms (Miami)
                - dfw: 135.6ms (Dallas)
                - den: 154.6ms (Denver)
                - blr: 162.8ms (Bangalore)
                - sfo: 170.1ms (San Francisco)
                - lax: 171.1ms (Los Angeles)
                - jnb: 174.5ms (Johannesburg)
                - sea: 175.8ms (Seattle)
                - sao: 210.6ms (São Paulo)
                - hnl: 222ms   (Honolulu)
                - sin:         (Singapore)
                - syd:         (Sydney)
                - tok:         (Tokyo)
                - hkg:         (Hong Kong)

Output of status:

x@tailscale:~$ tailscale status
100.xx.xx.63   tailscale            VioletFlare@ linux   -
100.yy.yy.99  desktop-gid8kj0      VioletFlare@ windows idle, tx 3932 rx 6132

I can make a TCP connection between these nodes with netcat and exchange messages.
What I cannot do is use netcat to exchange messages over UDP.

For instance, if I launch netcat to listen on UDP on my VM:

sudo netcat -ul 27960

then attempt to connect over UDP from the Windows 10 machine:

ncat -u 100.xx.xx.63 27960

and finally when i attempt to exchange messages nothing comes through.

Another thing I’ve noticed, the UDP services do not appear in the services section:


Meanwhile, listening on a TCP port with netcat shows a new service.

Is my connection not set properly?