Not a useless comment 
And I imagine that many are not familiar with SPIFFE or SPIRE. This video is an excellent overview of the architecture
https://youtu.be/ZJxq8hPgYVI?t=1
I do plan on writing the Spire LXD attestation plugin at some point. I actually think LXD is a great thing to integrate with SPIRE, because LXD has native support for TPM devices.
The plugin I authored before was for Puppet Bolt, which is similar to Ansible. Technically, I started writing the plugin, but Lucy and Tom and Puppet were kind enough to help me get my PR over the line.
Much like in the Bolt plugin case, it all started with a forum post and a crazy idea