When LinuxDeviceProcess (https://github.com/qt-creator/qt-creator/blob/master/src/plugins/remotelinux/linuxdeviceprocess.cpp#L76) tries to execute a remote command, the resulting command line is something like this:
In case of Raspberry Pi with default password the readAllStandardOutput() returns the following:
While the expected output for the user would be "MyCommand".
The default password warning comes from the " . /etc/profile" LinuxDeviceProcess prepended to user command and the 4521 from "cmd.addArgs("echo $$ && ", CommandLine::Raw);" which is used to parse the process ID.
What is more, thanks to the Raspberry security warning, the process ID parse actually fails in LinuxDeviceProcess::readAllStandardOutput() because only parses the first line of the output: