I just tried to boot with just the lid of the NESPi case removed, where the SATA-to-USB adapter is located, which was of course plugged into one of the Pi's USB 3.0 ports.

Now it boots without problems!

Since these problems started after I performed an update of RetroPie, I suspect an EEPROM update of the Pi made the SATA-to-USB adapter incompatible. I never would have suspected the case lid as it has worked without problems in the past.

At least we finally found the problem. I'll now try to fix this by updating the firmware of the adapter in the case lid and report back whether it worked.

Thanks for your help, mitu! :-)

@mitu Sorry for the late response!

There were indeed no events when I tested with evtest.

I completely removed the keyboard again, rebooted and started Pixel. I again paired the keyboard, and made sure it worked in Pixel. Then I rebooted into ES again, again no keyboard..... some kind of weird inspiration made me go to the Retropie Config (you know, where the setup.sh is started) and, much to my surprise, I found that after a few button pushes the keyboard started working! I have no idea what went on and why it worked, because apart from opening setup I did nothing differently from the first time. After leaving the config I started evtest again (via the remote console) and actually this time around the events were showing up! The keyboard actually started to work!

Soooo happy now, as after adding the proper event source to the moonlight config I actually have full keyboard support there as well!!!

Thank you again for your help and patience @mitu !

@JL-2600 UPDATE: I ending up trying to update to 4.6 again, but this time it updated only RetroPie and nothing else. Everything seems to be working just fine this time!

When I originally tried the update a few days ago, it also updated the emulators, so perhaps it was one of those emulator updates that was causing the problem.

Thanks!

@mitu Okay sounds good, I'll try doing a fresh install as you suggested. Thanks!

that's curious now.
I just altered the bluetooth connection method to "boot" (instead of background), and the nes30 pad always immediatly reconnects after pressing the power button.
I don't even have to wait a few seconds...

I'm pretty sure I tried that mode the first time as well... with very different result.

anyhow, still don't know how to figure out which firmware version is inside my 8Bitdo gamepad.