What a lot forget to take into account is that Matter relies on ipv6 and mDNS, which i tricky across VLANS because mostly (for matter) it is using the link local address, which not routable, which means link local can’t route acrosss VLANs. Not to say it is impossible to get Matter to work across VLANs, but it it wasn;t designed to work across VLANs.
Multi homing your HA instance is likely the best work around, but there is not going to be a 100% guarantee Matter devices will work across different VLANs without consdierable faffing around.
I am no expert in Matter of course, but this thread has some good information Home Assistant can’t add Matter devices that are in a different VLAN - Configuration / Matter/Thread - Home Assistant Community (home-assistant.io)