The standard linuxcnc_post.py shipped with FreeCAD should strip off all Fxxx from the G0 commands. I am sure that I never see a feedrate attached to a G0 command.
Are you using a custom postprocessor?
LinuxCNC does accept speed inputs (contrary to the comment in the linuxcnc_post.py), but with a condition.
This will produce coordinated motion to the destination point at the maximum rapid rate (or slower).
The maximum rate is limited by your LinuxCNC setup files, but you can make the rate smaller through the G0 command.
In general feed rates are modal; once set they continue until changed. However for G0 the feed rate is special, as noted above.
Gene