Thanks for the hint, but no, no mismatch and yes the files are being pulled (even looked with tshark if everything comes over properly).

The solution was then much more benign. The stock kernel in the NFSroot where the initrd was produced in was much smaller than the one from the bootable system. This lead into why this was the case and it was missing about 200 non-free drivers which somehow made the kernel stop right before really starting off.

Adding those to the NFSroot and then into the initrd solved the problem sigh

Wasted way too much time there and I still have no idea why 5.10 booted ok the whole time.

RAID5 ist auch mit SSD eine blöde Idee, solange das Dateisystem nicht selbst auch Prüfsummen schreibt. Ansonsten kann es passieren, dass ein Stripe nachher nicht mehr zusammenpasst, weil ein Device etwas falsches ohne Fehler liefert, dann aber das System/der Controler nicht mehr erkennen kann, welcher Block jetzt kaputt ist.

Daher mein Tipp: RAID6 oder ZFS.

paperless-ngx aufsetzen, einscannen, taggen und dann schnell wieder finden :)

https://www.debian.org/distrib/packages could be a place you may find it. But apt-file did not find it from my sources list, so I hope you will be luckier.

or if you are comfortable with command line and some replacement shenanigans, there is always mmv