"Nothing of the behavior for this should have changed in the last few releases with your configuration. We now explicitly install dnsmasq as a local resolver spawned by NM to facilitate handling DNS information when used with VPNs, and it does appear to work properly on my systems.
However, you're not using dnsmasq (missing dns=dnsmasq in /etc/NetworkManager/NetworkManager.conf) and have interfaces configured in /etc/network/interfaces.
Please try to reproduce the issue and include debugging logs (but make sure to clean them up first, as they may contain usernames, passwords, and other se…