I have a 5" touchscreen I'm trying to get to work. I initially had 7.02 running on RPi 1, without touchscreen support. To get that to work I followed another thread. It required going to Krypton so I upgraded to v7.90.007: the screen would work during boot (splashscreen) but then fade to white. It had worked on 7.02 and happened on a PC monitor as well, so it's not the cable/screen.
Next I installed v7.90.007 clean. I changed config.txt to include the hifiberry overlay. It booted fine and the screen worked. I set up wifi and adjusted some other settings: still working great. I rebooted: still doing fine. Next I selected the ALSA/hifiberry DAC: as soon as I did, the screen faded to white again. Remote control (official iPhone app) is unresponsive, but I can ssh and samba in.
Actually - the ssh and samba connections seemed to have died after a while. I then did a hard reset and it rebooted. The screen was working again, but the audio out had been changed. Setting it back to hifiberry, the screen went white again.
RPi 1 B
Amazon USB hub
5" HDMI interface screen (see here; it shows up as D_WAV Scientific Co., Ltd on lsusb - HDMI for signal, USB for power and touch signals)
EDIT: found kodi.log through samba - see here. Last message is to do with being unable to load skin settings.