I transfered the file
filename.gpx from Ubuntu 16.04 to mobile and get an error. In syslog I find:
Mar 10 10:24:55 lipa obexd: Transfer(0x5584ded061b0) Error: Unsupported Media Type
After that, I renamed file to
filename.txt and transfer was successful. Why there is restriction to send files with
.gpx (and maybe others) extension.