In Thread HA and VLANs - will this work? i’ve reported issues but got it to work now.
Network setup using Unifi hardware:
* Global settings for Gareway mDNS Proxy and IGMP Snooping : disabled/off
* VLAN1 (main - trusted) IPV4 192.168.10.x/24, IPV6 setup static, FDAA:x:x:0001::/64
* VLAN20 (family - trusted) IPV4 192.168.20.x/24, IPV6 setup static, FDAA:x:x:0002::/64
* VLAN30 (iot - untrusted) IPV4 192.168.30.x/24, IPV6 setup static, FDAA:x:x:0003::/64
* NO mDNS traffic allowed between VLAN30 and VLAN1
PVE setup
I am running my HAOS as VM on Proxmox PVE computers. HAOS is dual-homed to both VLAN1 and VLAN30:
untagged in vlan1: net0, bridge=vmbr0
tagged in vlan30: net1, bridge=vmbr0, firewall=1, tag=30
ZBT2 Antenna USB Device: host =####.####
My preferred setup is to connect USB devices to a dedicated RPI4 with Ser2net websockets to a VM. First I wanted to make sure Matter over Thread is working in HA.
added local conf settings to PVE in /etc/sysctl.d
net.ipv6.conf.vmbr0.autoconf = 0
net.ipv6.conf.vmbr0.accept_ra = 2
net.ipv6.conf.default.forwarding = 1
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.default.proxy_ndp = 1
net.ipv6.conf.all.proxy_ndp = 1
Matter devices in HA
To connect Matter, i am using a companion profile of:
Home Assistant URL: http://192.168.10.12:8123
Home Network: IOT network
Internal Connection URL: <empty>
and i have now 8 Ikea Matter devices connected 
CHECKLIST
This works but i am not fully done:
Setup HAOS for Matter Thread network
Connect ZBT2 to PVE host, HAOS VM. Autodetected in HAOS
Connect Ikea devices
Verify Matter and devices keep working after VM or PVE reboot
Adding new Matter devices works better after VM reboot.
Move ZBT2 connection from PVE + VM to a RPI with Ser2Net
Resolve connection issue (distance to Antenna?) of one device