The main HFS+ volume on macOS is no longer on a partition visible to Linux these days. It's a logical volume within Apple's volume manager, Core Storage.
/dev/sda2 409640 975503591 975093952 465G Apple Core storage
Is a core storage physical volume, not HFS+. Inside of it, is the HFS+ logical volume. Right now there's no native support for Core Storage in Linux. There is a project working on FileVault support, i.e. the encrypted variant of Core Storage volumes. I have no idea if that project can work if there's no encryption present. There is a lot of obfuscation here, Apple hasn't ever documented Core Storage format or function, and they haven't open sourced the code like they did with HFS+ in Darwin.