The question is quite common, but I have tried a thousand solutions that I found on the Internet and none of them has solved anything for me. The problem is that my laptop does not recognize any mobile, but for example an external hard drive has no problems, I can copy, delete files whatever. I have two ports, one 2.0 that does not leave the connection and ubuntu gives an error and another 3.0 that recognizes it in Windows but it comes out empty, no folder at all, and in ubuntu connects and disconnects or does not even connect. I have tried several phones and several cables and none of them work when they have gone without problems in other computers. I hope help, I am working with android studio and it is impossible to debug without having the phone connected.