And broken it is.
I found out I had many SPI CRC2 errors in my kernel logs.
Looking around I found this post
It turns out the stock image 20220412.0 for nodered actually ships with the broken revision 1.108 of the kernel module.
Thanks to @knebb 's instructions I was able to downgrade to v1.106 and my neuron seems to be working fine again.
I hope someone from the customer support gets to see this post and fixes the image quickly.
Guys, you have a terrific product line (I bought two neurons and some accessories over the years and I am a very happy customer), but you should really improve the regression testing before releasing: it is not the first time I have problems when trying to use an official image: see here
I might be able to provide you with some logs in case you need help in troubleshooting on older hardware (S103 S/N 109 from 2017): just contact me in the next couple of days - then I'll have to put the system back on the field.