Support for chattr +C/-C was added to e2fsprogs 1.42.4.
The most recent version of e2fsprogs is v1.42.6.
Debian is shipping e2fsprogs 1.42.5.
Note that e2fsprogs 1.42.x is a maintenance release, so it would be useful for an Ubuntu LTS to consider upgrading to a newer version of e2fsprogs, and to track the 1.42.x releases in general. (For example, I'm aware of a bug where users using the 64-bit feature of ext4 and fairly large RAID arrays can potentially lose data if they do an off-line resize using resize2fs. That fix will be in 1.42.7, once I get that fixed....)
Support for chattr +C/-C was added to e2fsprogs 1.42.4.
The most recent version of e2fsprogs is v1.42.6.
Debian is shipping e2fsprogs 1.42.5.
Note that e2fsprogs 1.42.x is a maintenance release, so it would be useful for an Ubuntu LTS to consider upgrading to a newer version of e2fsprogs, and to track the 1.42.x releases in general. (For example, I'm aware of a bug where users using the 64-bit feature of ext4 and fairly large RAID arrays can potentially lose data if they do an off-line resize using resize2fs. That fix will be in 1.42.7, once I get that fixed....)