@tlustoch
The node is a very simple one. So I never considered boot loaders, as the node would not need changing sketches during it's lifetime. I have boot loading functionality on my other designs, this one is a minimal board. Any extra chip would beat the purpose of the word "minimal".
It's a dumb node for a reason
this kind of optic fiber is probably only plastic so for a full DIY , you can use also fishing wire with a big power led or an old chistmass tree optic fiber lighted.....
@Zwer2k my expectations seem correct. I created a bug report that also includes a rudimentary workaround.
https://github.com/mysensors/MySensors/issues/1496#issue-968399284