@fortisy, you can create VLAN3 with the gateway IP Address of 192.168.3.1 and range of 192.168.3.4 to 192.168.3.99 (mask 255.255.255.0). That won’t conflict with your current 192.168.2.xxx LAN. Just change “2” in my example above to “3”.
Connect the AP One AX with an Ethernet cable to a Port on the router with Trunk as the Port Type (not Access as I stated earlier and will correct). Trunk is the default Port Type as I remember.
Then configure the AP One X with a newly created SSID (“Alphonse441”) and associate it with VLAN3. Connect your 3 TV’s wirelessly to Alphonse441. The Alphonse441 SSID will use DHCP to dynamically obtain their IP addresses using what you defined in VLAN3. Those addresses will be in the 192.168.3.XXX range. (I am assuming that your TV’s are defaulting to DHCP. I doubt they have an option to statically assign an IP address. But if they do and you are using it, then change their static IP address to something like 192.168.3.200, 201 and 202 so they aren’t in VLAN3’s dynamic range of 4 to 99.)
At this point, you will have two SSID’s on the AP One AX. The default and Alphonse441. The default SSID packets will be untagged and the Alphonse441 SSID packets will be tagged with VLAN ID 3. Since you have disabled “Inter-VLAN routing” on VLAN3, the TV’s won’t be able to talk with your LAN which is using untagged devices or your default SSID which is untagged. The TV’s will be able to talk to each other unless you enable Layer 2 Isolation on the Alphonse441 SSID.
The untagged devices on your LAN and the untagged devices on your default SSID will be able to talk to each other.
If you ever need to add a managed switch in between your router and your AP One AX, see Balance 20x & AP One AX Lite: VLAN question.