virtualbox.org

Same problem here, host: Ubuntu 20.04.3 LTS. It appears the vboxnet0 adapter is not even created.
As with all recent version upgrades, I knew the host-only network disappears and I had to recreate it when upgrading to 6.1.28.
Trying to set IP address, both via GUI and commandline, I got an error: Code E_ACCESSDENIED (0x80070005).
Unlike with all previous versions, the vboxnet0 adapter was not listed by ifconfig and trying to do anything on it yielded "no such device".
I reverted to 6.1.26 waiting for a fix.
Thanks
Marco

In my own setup, the VirtualBox Host-only Networking works as expected. That's why I've been asking for the configuration.

@mcontenti: Do not hijack other threads, create your own. Choose your title carefully.

fth0 wrote:Please post a zip file containing the contents of ~/.config/VirtualBox, which contains the configuration and log files for the Host-only Networking.

A minor hint just in case you don't have noticed it already: Note that both VirtualBox versions (6.1.26 and 6.1.28) only assign the IP address to a Host-only Adapter when the first VM using it is started, so don't check it too early.

This is a documented change in version 6.1.28, but pretty well hidden imho.

See changelog:

Network: More administrative control over network ranges, see user manual

We hit the same issue, but found out we can fix it as described here:

On Linux, Mac OS X and Solaris Oracle VM VirtualBox will only allow IP addresses in 192.68.56.0/21 range to be assigned to host-only adapters. For IPv6 only link-local addresses are allowed. If other ranges are desired, they can be enabled by creating /etc/vbox/networks.conf and specifying allowed ranges there. For example, to allow 10.0.0.0/8 and 192.168.0.0/16 IPv4 ranges as well as 2001::/64 range put the following lines into /etc/vbox/networks.conf:

* 10.0.0.0/8 192.168.0.0/16
* 2001::/64

Please see viewtopic.php?f=7&t=104198 where the info above from 'challengeursli' and some more bug workaround from 'aleksey-vb' gets host-only networks working again.