for my (Frank-Uwe) PC it like this:
xfreerdp /u:dill /d:win /size:1900x1100 /v:hasp116fud
If there is a message like this:
The fingerprint for the host key sent by the remote host is
Please contact your system administrator.
Add correct host key in /home/p01user/.config/freerdp/known_hosts to get rid of this message.
Open the known_hosts file and delete the complete content. Do not forget to save the file.