There was discussion in Discord about removing this demo site.
If what we need is to be able to link to a classic UI demo site, then the Plone 6 classic UI demo site would suffice, correct?
Also to consider how long 5.2 will be officially supported.
I'm going to remove the link to the 5.2 demo in Plone 6 Documentation so that our CI stops failing.
I think it makes sense to stop promoting a demo of a version which is now in the "security support" phase of maintenance (Release Schedule).