Ubuntu 21.10 - Netplan: object has no attribute 'state'
There is a bug report about this issue with 'netplan try' https://bugs.launchpad.net/ubuntu/+source/netplan.io/+bug/1949104
As a workaround you can execute the "netplan try" command as:
netplan try --state /etc/netplan
This will mitigate the problem for the time being.