If I we can't have them solder the display on the PCB for us, and have to get it separately, maybe we can at least skip the soldering step by using an FPC connector. This way you just have to stick the display in the, insert it into the connector and you are done. The Nokia display has a 12-pin FPC ribbon, with 0.6mm pitch. Looking through LCSC, there are no 12-pin connectors in that pitch, but there is a 13-pin one. A bit of a weird number, but maybe we can shift the ribbon to one side and still use it. So I ordered it to see how it will work mechanically. Three weeks later it arrived, and I have to say I didn't expect this:
A bit small, isn't it? You see, it does have 13 pins, but six of them are on the bottom, while seven are on the top side of the ribbon, alternating. That does explain why all those connectors have an odd number of pins.
But that means we need either a 23 or 25 pin connector, depending on whether the contacts are on top or bottom. A search through LCSC reveals that the 25 pin connector has been discontinued, so that leaves us with the 23-pin one. No problem, we can manage that by threading the FPC ribbon through a hole in the PCB without bending, and having the connector on the other side.
There is only one more problem left. That connector costs $0.50 a piece – it doesn't seem like that much until you realize it's half the price of the display. Ooof. I will keep exploring the possibilities.