A recent example: throwing food down the drain. Are this question and others about properly disposing of food waste on topic?
Yes. This is essentially an equipment and cleaning question. Equipment is mentioned in our top-level site scope as being on topic. Cleaning is a common topic in its own right, as evidenced by the 146 questions tagged [cleaning], and often intersects with equipment. And of course, properly disposing of food waste is an integral part of cooking - it's nearly impossible to cook without doing this - so it makes sense that it's part of our scope.
A great example of a well-accepted previous question in this vein is What's the proper way to dispose of used fats & oils?. The recent one about food down the drain isn't as well-written, and it's phrased more as "how do pipes work?" instead of "what should I put down the drain?", but it's a similar kind of question, and is no less on topic.
No, it is not on topic.
It is NOT essentially a cleaning and equipment question. If it were, it comes down to "what are the proper methods to dispose of the waste" or "what types of waste is it permissible to dispose of down the drain", either of which would be on topic.
However, what it is asking is why is it or is not appropriate to put things down the drain, which is a question of how the sewer system works, and local regulations. That is not a culinary question.
The only answer so far does not contain any culinary or kitchen management information--it is all about what happens in the pipes and sewer system, which is not in my opinion on topic.