Unanswered New Screen Troubles

If you use that screen I am not sure the existing drivers for the 3.5 inch screen will work.
You will probably need to installed the drivers for that one.

That is probably the same as the 7" Waveshare: https://www.waveshare.com/wiki/7inch_HDMI_LCD_(B)

 

Raspbian has those drivers by default, but the Robo image with OctoPi and the LCD software would use a different driver for that 3.5" screen so you need to install the drivers for that one back

 

and as a TOTAL side note -- this is why Robo should never have gone down this road -- they are not software people and when you have an OS involved things get complicated They had enough issues dealing with Marlin much less Raspbian, OctoPrint and the custom menu stuff...