WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
It has very high amplification factor (160) so anode current depends heavily on grid voltage and only weakly on anode voltage. Notice too that under normal conditions the grid is positive, so you could say that it is acting more like a screen grid. It is a 'zero bias Class B' triode, so you use it in much the same way as you would with g2 drive to a normal pentode.
Mu doesn't really mean very much for pentodes; you have instead to think about inner mu and outer mu. To get triode-like curves you would need a rather loose g2 pitch, which means it isn't really working as a pentode.
A penthode in UL-configuration also acts more or less like a triode,depends on where the tap is placed.At the + it's a penthode,on top it's a triode (anode connected to g2)and ererything in between