Follow steps 1-3 here: https://www.howtogeek.com/276468/how-to-use-a-raspberry-pi-as-a-networked-time-machine-drive-for-your-mac/
Then:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install hfsplus hfsutils hfsprogs gdisk
- To add HFS/HFS+ support to RPi