On my Ubuntu, the directory in which pluggable media is mounted (/media/me) is owned by root and has access flags drwxr-x---+, so without the "alternate access control method" indicated by the + I wouldn't be able to access it.
How I can I determine which access control method is used and where it is set?
getfacl /media/me(aclpackage, see also theaclman page). I'm not aware of other methods supported by Ubuntu. – Stéphane Chazelas Aug 22 '18 at 23:06