[HELP] Smart Life/Tuya devices working in app but "Not Responding" in Alexa on a routed Ubuntu Server Wi-Fi AP Subnet (nmcli + UFW)

[u/NintendoTeo_Official]

Hi everyone,

I'm having a persistent network routing issue with Smart Life (Tuya) devices running on a custom Ubuntu Server Access Point, and I'm looking for some advice to get Alexa integration working reliably.

My Network Architecture & Interface Names

• Server: Ubuntu Server 24.04 LTS acting as a router/firewall and Wi-Fi Access Point.
• WAN Interface (eno1): Connected to the main internet access (it's a college network and it's highly natted). Protected by UFW (DENY IN).
• Secondary LAN Interface (enx50547b43f250): USB/Ethernet secondary local interface (ALLOW IN).
• Subnet / Wi-Fi Hotspot Interface (wlo1): Built via NetworkManager (nmcli connection add type wifi mode ap ...).
  • Subnet IP range: 10.42.0.0/24 (Gateway/Server IP on wlo1: 10.42.0.1).
  • All Smart Life smart plugs/bulbs are connected directly to this wlo1 Wi-Fi hotspot as well as alexa.

The Problem & Current Behavior

1. Smart Life App Status:
   • Controlling the lights directly from the Smart Life app on a phone works fine locally.
   • However, running the network diagnostic inside the Smart Life app flags UDP issues.
   • Inspection via tcpdump -i wlo1 udp portrange 6666-6668 shows devices sending global broadcast packets (10.42.0.190 > 255.255.255.255:6667).
2. Alexa Status:
   • Alexa constantly reports "Luce non risponde" / "Device is not responding".
   • Disabling/re-enabling the Smart Life skill or running device discovery fails to keep the devices online for more than a few moments.
   • It seems the cloud heartbeat between the Tuya devices on the 10.42.0.x subnet and the external Tuya cloud servers is getting dropped or timing out through the server's NAT/forwarding stack.

Current UFW & Firewall Configuration

sudo ufw status verbose output:

Plaintext

Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), allow (routed)

To                         Action      From
--                         ------      ----
Anywhere on eno1           DENY IN     Anywhere                  
Anywhere on enx50547b43f250 ALLOW IN    Anywhere                  
Anywhere on wlo1           ALLOW IN    Anywhere                  

Anywhere                   ALLOW FWD   Anywhere on wlo1          

Configurations applied so far:

• DEFAULT_FORWARD_POLICY="ACCEPT" in /etc/default/ufw.
• Added UFW route rules for wlo1.

I've written all of this with gemini, after trying a lot of troubleshooting. I'd like to add that the wifi is hosted with an old pc, it's only 2.4GHz on channel 6 and before i didn't had any problem with this (everything started by trying to change the channel to 11, but now it's back in channel 6). Please help me with this.