Something important that may be overlooked in the blog post is that for most bands you need licenses to transmit over the air. ISM bands are unlicensed but may come with other limitations (e.g., in some countries regulators require a listen-before-talk mechanism that is not always implemented in cellular stacks).
All the examples in the blogpost is areas where you own the property, and in most countries can deploy this if you are careful not to interfere with areas outside of your property. With 5G this is easier because you can use ISM bands within the “core” and WiFi closer to the edge.
Something important that may be overlooked in the blog post is that for most bands you need licenses to transmit over the air. ISM bands are unlicensed but may come with other limitations (e.g., in some countries regulators require a listen-before-talk mechanism that is not always implemented in cellular stacks).