The issue was fixed by changing the MAC address of the virtual machine - seems like not related to the upgrade at all.
Further inspection discovered that ARP replies were not arriving inside the VM - they were visible in tcpdump on the bridge as well as both member interfaces, but not inside the guest os.
Tried clearing arp cache in the vm, on the opnsense host and on the switch that sits between opnsense and other machines in the subnet, did not help.
I spun a second vm and this one got all the networking working fine, so I decided to get new MAC address for the original vm and that solved the problem.
Still have no idea what was the root cause of such behaviour, but at least it's working now.
Further inspection discovered that ARP replies were not arriving inside the VM - they were visible in tcpdump on the bridge as well as both member interfaces, but not inside the guest os.
Tried clearing arp cache in the vm, on the opnsense host and on the switch that sits between opnsense and other machines in the subnet, did not help.
I spun a second vm and this one got all the networking working fine, so I decided to get new MAC address for the original vm and that solved the problem.
Still have no idea what was the root cause of such behaviour, but at least it's working now.
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