Update 2022-07-14: kill kiod or kiod5 and then do jmtpfs
Update 2021-07-10: sudo aptitude install gmtp
It can be a challenge to mount your Android phone (MTP device) in Linux if you have some strange files from your old Iphone. I needed to do it the hard way.
You need to install mtpfs and use this command: sudo mtpfs -o allow_other /media/android-device