The industry-wide supply chain issues continue to hit prospective Apple customers looking to buy new Macs. Today, the base model $599 M4 Mac mini with 256 GB storage is now completely out of stock at the Apple Store. That means Apple won’t let you order it at all, simply stating it is “currently unavailable” for delivery. In fact, the situation is actually more dire. It turns out any M4 Mac mini with 256 GB storage is now in the same boat, regardless of RAM configuration. (Third-party retailers aren’t faring much better: Amazon only has M4 Pro Mac minis on sale now ). It feels like every week the availability of the current lineup of Mac desktops gets worse. On April 11, we reported that Mac mini with 32 GB and 64 GB RAM options were no longer available to buy. Now, even more models are unavailable, with the base 256 GB storage option seemingly gone from Apple’s shelves. Stock of other models is not exactly plentiful either.…