It’s the Linux kernel update. From the [nerves_system_rpi3/CHANGELOG.md at main · nerves-project/nerves_system_rpi3 · GitHub]:

• Switch from the Raspberry Pi’s deprecated MMAL media support to DRM and libcamera. This is a big change if you use the display or camera that has been a long time coming. Please plan some time to make the upgrade.

In theory, you could backport the OTP 27 update to the nerves_system_rpi3 v1.27.1. It’s not that complicated, but not worth the time.

Could you create an issue to track the console for the touchscreen?

I took a quick look. I only use the RPi3 headless, but if I were to take a first guess, I’d modify the config.txt (just manually do it by mounting the boot partition of the MicroSD card on your build machine) and add this:

# Automatically load overlays for detected DSI displays
display_auto_detect=1

and also copy vc4-kms-dsi-7inch.dtbo into the overlays directory. It’s probably going to take a couple iterations and starting a GitHub issue seems like a better place to iterate. If that doesn’t work, try copying all of the dtbo files into the overlays directory. If that doesn’t work, then I’d run Raspberry Pi OS and run lsmod to see what kernel drivers are loaded and then run lsmod on Nerves and compare. It won’t be the same, but I’d expect a difference in vc4 drivers.

Sorry to give so many instructions. I think a lot of the Nerves core team is traveling or prepping for travel right now with out Raspberry Pi 3’s on hand. It definitely looks like something was missed on the big MMAL->DRM update for RPi3, though.

GH Issue for reference:
https://github.com/nerves-project/nerves_system_rpi3/issues/336

Got it!

The display stops working between commits 1712c7c6ea4ed0ece8a560a6daf7087d5b86f70c "Only trim serial number for hostname" and e0c89818e4192b469a502ee7e9cb480756ffef16 "Update to Linux 6.6, DRM, and libcamera".

The most obvious culprit is a linux defconfig change with the working commit having CONFIG_FRAMEBUFFER_CONSOLE=y set and the later commit having this option removed.

I’ll build a new custom system based on 1.8.1 with this option set tomorrow to verify.

I’m still wondering, though, if this change was intentional. From my understanding, this should also apply to HDMI output.