Vlan passing problem

Hello guys!

Just a small disclaimer: My problem is actually not related to the UTM at all (other than the fact that I am creating a vlan in the UTM). However posting here in hope someone can help since this forum has a lot knowledgeable and nice people

First let me attach a basic network diagram of what I have:

So I have created a vlan (vlan10) on the utm. Added a new DHCP server for this vlan etc

The UTM is connected to  a dumb unmanaged linksys switch. On the same switch I have a unifi Access Point. On the AP I created a secondary guest wifi network that uses vlan 10.

When I connect to that ssid all is good, I get an IP address from the DHCP server of Vlan10 and all. So the dumb switch actually passes through the vlan to the AP without any issues.

This unmanaged switch is connected to a TP-Link homeplug and this gives network to the other side of the house, in my bedroom,  where I also have my tiny home office.

There is another homeplug in the bedroom that is connected to a managed switch (HP procurve) on port 2. On the HP switch, I have various systems connected, including a secondary Unifi AP

If I try to connect directly to the secondary AP, that is in my bedroom, but connect to the guest SSID (vlan10), I never get an IP address from the DHCP server of vlan10.

So the vlan seems not being passed to the bedroom side of the house

On the managed HP switch I have created vlan10 and assigned port 23 to that vlan. Connecting my laptop to the port result in no ip address for the laptop. Assigning a static IP on the vlan10 subnet on the laptop results to nothing ( I cannot ping vlan10 gateway IP)

Additionally tagging port 2 on the HP switch to carry both vlans (the default and vlan10) breaks all connectivity to the UTM side of the house

My best guess is that I need to replace the linksys switch with a managed one and tag the port that goes to the living room homeplug with both vlans (??)

That was my intention from the start (ie to have managed switches on both sides in order to use vlans), but then I realized that the AP which is connected to the dumb switch gets the vlan information without issue, so the dumb switch seems to pass the vlan information just fine... In this regard, I thought that tagging the uplink port on the HP switch (creating a port trunk in Cisco language) would do the trick, but as I mentioned, this breaks all connectivity to the "left" side of the network.

Any insights welcome..

Thanks a lot!