I’d like my OS disk to be encrypted. It stores SSH keys, WireGuard configs (keys) etc.
I expect to unlock it via entering a password on keyboard each boot just like LUKS.
Unfortunately this doesn’t seem to be supported. Any workarounds?
Expand your setup, when you say OS Disk is this a virtual machine running on Truenas ?
Sounds like the risk you are trying to protect against is someone physically taking the system and extracting the credentials and there is not really any officially supported way to mitigate that.