320x240 dot matrix LCD power connection
These displays use a negative supply of something like -25V for the LCD. There is a pot from that supply to Vss (10K or 20K) to adjust the contrast. Typically Vdd-Vo is 23V at 25°C so the voltage at the pot wiper would be about -18V. The pot is used to adjust the contrast to compensate for variations from glass to glass variations and with temperature and voltages and viewing angle.
As @jonk says, this one appears to have a DC-DC converter to generate the negative voltage, so you should only need to supply +5 and the backlight current, which is quite nice compared to some competitive panels.
See below. The green arrow and circle show you the controller which you must also track down in order to work out the details of communicating with the LCD display. (See link to controller below picture here.) The red arrow points to where you can spot the potentiometer being used for contrast control. Take note that it appears that \$V_\text{EE}\$ is an output of their power module, so it's providing a convenient negative voltage source for your use with the potentiometer. Another red ellipse circles \$V_\text{EE}\$ on the pinout.

Most of the information you need to use them is in the datasheet for the controller.
You can also find libraries that support the controller (which is a Taiwan clone of the Epson SED1335), so you don't have to write all that code yourself.
I don't think it would be a huge deal to get this going, subject to the usual risk in dealing with Aliexpress sellers.