I was suspicious of CDNs right from the start. If they stop working, all examples are no longer immediately executable.
I therefore decided back in 2017 to save the required sources of three.js in the respective revision locally for my collection. Likewise other resources. Of course, this takes some work.
If you download the zip file of a vintage of the collection, you can be sure that all examples will work permanently. (The basic examples, the extended ones are only links, and mostly with the use of CDNs).
Unless the browsers have new requirements again, as was the case with older examples with video texture. They no longer work because user interaction is now required.