Sorry, I jumped the gun and have to retract my answer at the bottom of this post.
When a question is off topic (but not covered by a custom reason), the proper course of action is to select 'other' which will ask you explain why the question should be closed… which will allow others to select that reason and post it as a comment.
Closing as 'other' actually displays that same text as the original "standard blatantly off-topic" reason, but now the closure is accompanied by an explanation why that post was closed specifically.
The thinking in removing the default use case is that advanced communities should be able to explain why a post is being close rather than falling back on a reason that says little more than "this just doesn't fit…" If you feel a post should be closed, you should be able to explain why it should be closed. Using the 'other' close reason simply enforces this.
I added another custom close reason with the default text that came with the site:
This question does not appear to be about hardware recommendations within the scope defined in the help center.
Try not to overuse this. The default close reason that came with your site says little more than "this just doesn't fit" — but the thinking is that if you're already adding custom close reasons, you should be able to explain why something doesn't fit by selecting 'other' and leaving a clear comment. If that default close reason is used too often out of default-laziness, I will probably be asked to remove it.