I did some more testing (not using C-n/C-p much myself, mainly care about the other bindings) - C-p reliably works for me, C-n is sometimes weird. Which is a bit weird, as some of the other keybindings are also masking Firefox keybindings - like C-f, which reliably works.
Main problem is that they still don't have an API for doing keybindings after all those years, so as a result of that we have to run in the context of a website for each tab, which limits what is possible. There are a bunch of workarounds to make it useable - but also a bunch of things which just keep breaking.
Aber vieles davon tut dann halt weh. Falls man blind tippen kann ist Texteingabe ohne eine ordentliche Tastatur schrecklich langsam, und ein Bildschirm in halbwegs akzeptabler Groesse hilft auch. Gibt auch genug Sachen die ich auch am Notebook schon nicht machen will weil das mit mehr als einem Bildscheirm einfach komfortabler ist.