In case it is helpful to someone, this is how I could install the apfs-fuse suggested by telcoM, in Ubuntu 16.04:
sudo apt install fuse libfuse-dev bzip2 libbz2-dev cmake g++ git libattr1-dev
git clone --recursive https://github.com/sgan81/apfs-fuse.git
cd apfs-fuse
mkdir build
cd build
cmake ..
Ubuntu 16 has fusermount version 2.9.4, which needs adapting the make file to "change the option USE_FUSE3 to OFF" as explained in the readme file.
sed -i.bak 's/USE_FUSE3:BOOL=ON/USE_FUSE3:BOOL=OFF/' CMakeCache.txt
or it can be done through a ncurses GUI:
sudo apt install cmake-curses-gui
ccmake .
Finally:
make
sudo cp apfs* /usr/local/bin/
To mount :
apfs-fuse /dev/$diskpart $mountpoint
And fusermount -u $mountpoint to unmount.
Note that it is read-only for now.