I recently replaced Mint with Ubuntu 17.10 on my MacBook (2008) and have noticed that some symbol keys are not properly assigned (namely those between shift and Enter and the letter keys).
Can you help me?
You could switch to ISO layout instead of default by entering following in a terminal:
echo 0 | sudo tee /sys/module/hid_apple/parameters/iso_layout
Note: rebooting will reset this to default.
If everything works like you expect after this command, you can set it permanently using
echo options hid_apple iso_layout=0 | sudo tee -a /etc/modprobe.d/hid_apple.conf
sudo update-initramfs -u -k all
and eventually reboot your Mac.