Here, have a fresh Linux™ Age Verification™ API: { test -a ~/.dob && cat ~/.dob } || echo 1900-01-01
Conveniently, every system in existence is already compliant. How fortunate.
I find it hard to imagine any way to make it difficult to circumvent age checks by software the user runs, given the virtualization capabilities linux now has. Maybe if unprivileged user namespaces were disabled? Even if the kernel added a dedicated system call just for checking the current user's age, ptrace is a thing. That's not even getting started on the possibilities of things like LD_PRELOAD or outright modifying the program. And of course, there's always the nuclear option of just running the program in qemu.