Comment 1 for bug 1880627

This is resolved on the Ubuntu Server for Pi images; /dev/spidev.*, /dev/gpiochip*, and /dev/i2c-* are now accessible by members of the "dialout" group which the default user is added to by cloud-init.

Unfortunately, it's not yet resolved on Ubuntu Desktop for Pi as although the permissions are correct there, the default user is not a member of the "dialout" group. However, at this point this bug is now effectively a duplicate of 1923363, so I'll mark it as such.