I installed Anaconda which defaulted to creating /opt and installing everything there. I decided to delete it but now cannot remove the empty /opt directory no matter what I do. I have tried EVERYTHING, including everything mentioned on this page as well as xattr, Setfile, chflags, booting in single user mode, disabling SIP, enabling full disk access via System Preferences. I keep gettting the error 'operation not permitted'. I don't want to wipe the whole drive and start again, but this is really annoying.