Urgently searching a touchscreen which is 3.5 inch or smaller!
I haven’t found one with touch functionality via USB. It seems to be a feature available only for screens 5 inch or higher (because of size/cost?). Or has someone found such a touchscreen, there has to be something!
Most screens of smaller size will utilize GPIO and hence need custom drivers or did someone succeed to make a GPIO based touchscreen work?
I know the opinion of a lot of developers here is that a screen with such a size is not very useful. But I have to counter, a lot of bought screens are 3.5 inch or smaller, so they fit on the Raspberry Pi via GPIO and there were a lot of smartphones with such screen sizes in the early days. 
In my case, I want to develop apps, hence I can create a design working well on those screens and I need the a small form factor.
I will try to contribute here as much as possible during the time.
One first addition to the forum, as I think no one has tried yet with the DFRobot 2.8 screen: I couldn’t make it work, but it seems to be somewhat questionable, if it would be even supported with my Raspberry Pi 3 B+.