Is it ok to cross post a question here and on unix/linux stack exchange? My question relates to the apt package manager, so I would think it should be equally on topic there. Or is there a community view (in either community) against that?
Is it ok to cross post a question here and on unix/linux stack exchange?
No, because it is not OK to cross-post on U&L.
We don't have a formal cross-posting policy here (Ghanima may care to contradict me on that point), and my own personal feeling about it is that it should be okay if you include a link to all the places you've posted something in the post itself, clearly and explicitly, and not just SE sites (e.g., I believe in theory cross-posting here and on the Foundation's forum should be okay, but again, you should indicate this both places to show respect for the communities).
However, that's not the model officially used on most SE sites including U&L, and respect that, so please don't.
If a reasonable period of time goes by (say a day or so) and you have not received the attention you were looking for in the first place you ask, you can always delete that and ask somewhere else. If you can't delete it (e.g., because there are already upvoted answers), you can always edit into the question that you have moved your inquiry somewhere else (in which case your Q will probably be closed, and you should flag it for such).