Let's keep this one simple.

We all know there's an "any primal" and an "any piebald" filter in the TC, why not "any lethal"?
There are WAY more lethal mutations than primal variants, yet they still give us the option to select it.

While they aren't technically "variants", most people group them together.

I don't think this will be hard to implement, considering there's already two filters just like it.