Network interface not found error after upgrading to 6.1.0

[Stooxie]

After upgrading to VB 6.1.0 and still with 6.1.2 I get the following error when trying to start both Windows and Linux VMs:

Could not start the machine Linux OBI 7.2.64.0 because the following physical network interfaces were not found: en4: Thunderbolt Ethernet Slot 2 (adapter 1) You can either change the machine's network settings or stop the machine.

This always worked before. This is a MacOS Catalina host (10.15.2) using a wired ethernet connection off a Thunderport dock. The interface name is "en4: Thunderbolt Ethernet Slot 2". I am using this in bridge mode. Switching to NAT works fine.

[Jan Olsen]

Setting the interface to NAT does not work for me either. The VM starts, but no network connections are available.

en4 is up an running with

en4: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
	options=40b<RXCSUM,TXCSUM,VLAN_HWTAGGING,CHANNEL_IO>
	ether (MAC) 
	inet6 fe80::(MAC)%en4 prefixlen 64 secured scopeid 0xf 
	inet 192.168.1.107 netmask 0xffffff00 broadcast 192.168.1.255
	inet6 2003:c4:b70c:aefa:(MAC) prefixlen 64 autoconf secured 
	inet6 2003:c4:b70c:aefa:(MAC) prefixlen 64 autoconf temporary 
	nd6 options=201<PERFORMNUD,DAD>
	media: autoselect (1000baseT <full-duplex,flow-control,energy-efficient-ethernet>)
	status: active

Only solution to get the network running is to enable (and use) wifi.

[DallasBW]

Still unresolved with 6.1.4 and accompanying extension pack.

[sbates]

Still unresolved with 6.1.8 and accompanying extension pack.

[DallasBW]

Still unresolved with 6.1.10 and accompanying extension pack.

[DallasBW]

Still unresolved with 6.1.12 and accompanying extension pack.

[Aleksey Ilyushin]

Please provide VM's VBox.log, as well as the output of "VBoxManage list bridgedifs".