The problem becomes that not everything can be feasibly boiled down to purely true or false accuracy.
If you ask me how much is in my bank account, and I tell you it was $50 last time I checked, but I knew a $2000 deposit was coming, did I lie?
If you ask me about whether UFOs are real, and I tell you I've never seen one or met someone who credibly has, but I know we have a classified "Earth-Vulcan Treaty Negotiation" committee, did I lie?
If you ask me about the existence of programs to assassinate a dozen foreign leaders, and I answer 10 of them don't exist and say the answer to 2 are classified, but I know all 12 don't exist, did I lie?
It all goes down a rabbit hole of agency, intent, provability, and expected perception of what you communicated.
You can have secrets without having lies. Observe:
"What is the top speed of an F-16 fighter jet?"
"That information is classified."
I'm not entirely convinced there's any case where lying is required.