Using Homebrew, install osxfuse and ext4fuse
$ brew cask install osxfuse
$ brew install ext4fuse
Find the Raspberry Pi’s partition ID
$ diskutil list
Create a mount point
sudo mkdir /Volumes/rpi
Mount the drive
sudo ext4fuse /dev/disk2s2 /Volumes/rpi -o allow_other
Unmount the drive
sudo umount /Volumes/rpi
Tribute to Jeff Geerling https://www.jeffgeerling.com/blog/2017/mount-raspberry-pi-sd-card-on-mac-read-only-osxfuse-and-ext4fuse