If you don't fancy plain Debian, Linux Mint also have a release based on Debian though it gets less development than their main Ubuntu-derived version, but Debian is a slow release anyway.
I don't know if it'll work for a Mac, but for my old Dell 2-in-1 tablet I installed Linux Mint Debian Edition to get 32bit grub installed and then resized the partition to install Zorin next to it - luckily, Zorin detected the existing grub and and just added its own config files rather than trying to reinstall 64bit grub, so it boots fine.